// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains the logic to work with MPEG Program-Specific Information.
 * These are defined both in ISO/IEC 13818-1 (systems) and ETSI EN 300 468.
 * PSI is carried in the form of table structures, and although each table might
 * technically be broken into one or more sections, we do not do this here,
 * hence 'table' and 'section' are interchangeable for vidtv.
 *
 * Copyright (C) 2020 Daniel W. S. Almeida
 */

#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__

#include <linux/bcd.h>
#include <linux/crc32.h>
#include <linux/kernel.h>
#include <linux/ktime.h>
#include <linux/printk.h>
#include <linux/ratelimit.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/time.h>
#include <linux/types.h>

#include "vidtv_common.h"
#include "vidtv_psi.h"
#include "vidtv_ts.h"

#define CRC_SIZE_IN_BYTES 4
#define MAX_VERSION_NUM 32
#define INITIAL_CRC 0xffffffff
#define ISO_LANGUAGE_CODE_LEN 3

static const u32 CRC_LUT[256] = {
        /* from libdvbv5 */
        0x00000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9, 0x130476dc, 0x17c56b6b,
        0x1a864db2, 0x1e475005, 0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61,
        0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd, 0x4c11db70, 0x48d0c6c7,
        0x4593e01e, 0x4152fda9, 0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75,
        0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011, 0x791d4014, 0x7ddc5da3,
        0x709f7b7a, 0x745e66cd, 0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
        0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5, 0xbe2b5b58, 0xbaea46ef,
        0xb7a96036, 0xb3687d81, 0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
        0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49, 0xc7361b4c, 0xc3f706fb,
        0xceb42022, 0xca753d95, 0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1,
        0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d, 0x34867077, 0x30476dc0,
        0x3d044b19, 0x39c556ae, 0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072,
        0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16, 0x018aeb13, 0x054bf6a4,
        0x0808d07d, 0x0cc9cdca, 0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde,
        0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02, 0x5e9f46bf, 0x5a5e5b08,
        0x571d7dd1, 0x53dc6066, 0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
        0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b, 0xbb60adfc,
        0xb6238b25, 0xb2e29692, 0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6,
        0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a, 0xe0b41de7, 0xe4750050,
        0xe9362689, 0xedf73b3e, 0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2,
        0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686, 0xd5b88683, 0xd1799b34,
        0xdc3abded, 0xd8fba05a, 0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637,
        0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb, 0x4f040d56, 0x4bc510e1,
        0x46863638, 0x42472b8f, 0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53,
        0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47, 0x36194d42, 0x32d850f5,
        0x3f9b762c, 0x3b5a6b9b, 0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
        0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623, 0xf12f560e, 0xf5ee4bb9,
        0xf8ad6d60, 0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
        0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f, 0xc423cd6a, 0xc0e2d0dd,
        0xcda1f604, 0xc960ebb3, 0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7,
        0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b, 0x9b3660c6, 0x9ff77d71,
        0x92b45ba8, 0x9675461f, 0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3,
        0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640, 0x4e8ee645, 0x4a4ffbf2,
        0x470cdd2b, 0x43cdc09c, 0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8,
        0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24, 0x119b4be9, 0x155a565e,
        0x18197087, 0x1cd86d30, 0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
        0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 0x2497d08d, 0x2056cd3a,
        0x2d15ebe3, 0x29d4f654, 0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0,
        0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c, 0xe3a1cbc1, 0xe760d676,
        0xea23f0af, 0xeee2ed18, 0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4,
        0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662,
        0x933eb0bb, 0x97ffad0c, 0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668,
        0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
};

static u32 dvb_crc32(u32 crc, u8 *data, u32 len)
{
        /* from libdvbv5 */
        while (len--)
                crc = (crc << 8) ^ CRC_LUT[((crc >> 24) ^ *data++) & 0xff];
        return crc;
}

static void vidtv_psi_update_version_num(struct vidtv_psi_table_header *h)
{
        h->version++;
}

static u16 vidtv_psi_get_sec_len(struct vidtv_psi_table_header *h)
{
        u16 mask;
        u16 ret;

        mask = GENMASK(11, 0);

        ret = be16_to_cpu(h->bitfield) & mask;
        return ret;
}

u16 vidtv_psi_get_pat_program_pid(struct vidtv_psi_table_pat_program *p)
{
        u16 mask;
        u16 ret;

        mask = GENMASK(12, 0);

        ret = be16_to_cpu(p->bitfield) & mask;
        return ret;
}

u16 vidtv_psi_pmt_stream_get_elem_pid(struct vidtv_psi_table_pmt_stream *s)
{
        u16 mask;
        u16 ret;

        mask = GENMASK(12, 0);

        ret = be16_to_cpu(s->bitfield) & mask;
        return ret;
}

static void vidtv_psi_set_desc_loop_len(__be16 *bitfield, u16 new_len,
                                        u8 desc_len_nbits)
{
        __be16 new;
        u16 mask;

        mask = GENMASK(15, desc_len_nbits);

        new = cpu_to_be16((be16_to_cpu(*bitfield) & mask) | new_len);
        *bitfield = new;
}

static void vidtv_psi_set_sec_len(struct vidtv_psi_table_header *h, u16 new_len)
{
        u16 old_len = vidtv_psi_get_sec_len(h);
        __be16 new;
        u16 mask;

        mask = GENMASK(15, 13);

        new = cpu_to_be16((be16_to_cpu(h->bitfield) & mask) | new_len);

        if (old_len > MAX_SECTION_LEN)
                pr_warn_ratelimited("section length: %d > %d, old len was %d\n",
                                    new_len,
                                    MAX_SECTION_LEN,
                                    old_len);

        h->bitfield = new;
}

/*
 * Packetize PSI sections into TS packets:
 * push a TS header (4bytes) every 184 bytes
 * manage the continuity_counter
 * add stuffing (i.e. padding bytes) after the CRC
 */
static u32 vidtv_psi_ts_psi_write_into(struct psi_write_args *args)
{
        struct vidtv_mpeg_ts ts_header = {
                .sync_byte = TS_SYNC_BYTE,
                .bitfield = cpu_to_be16((args->new_psi_section << 14) | args->pid),
                .scrambling = 0,
                .payload = 1,
                .adaptation_field = 0, /* no adaptation field */
        };
        u32 nbytes_past_boundary = (args->dest_offset % TS_PACKET_LEN);
        bool aligned = (nbytes_past_boundary == 0);
        u32 remaining_len = args->len;
        u32 payload_write_len = 0;
        u32 payload_offset = 0;
        u32 nbytes = 0;

        if (!args->crc && !args->is_crc)
                pr_warn_ratelimited("Missing CRC for chunk\n");

        if (args->crc)
                *args->crc = dvb_crc32(*args->crc, args->from, args->len);

        if (args->new_psi_section && !aligned) {
                pr_warn_ratelimited("Cannot write a new PSI section in a misaligned buffer\n");

                /* forcibly align and hope for the best */
                nbytes += vidtv_memset(args->dest_buf,
                                       args->dest_offset + nbytes,
                                       args->dest_buf_sz,
                                       TS_FILL_BYTE,
                                       TS_PACKET_LEN - nbytes_past_boundary);
        }

        while (remaining_len) {
                nbytes_past_boundary = (args->dest_offset + nbytes) % TS_PACKET_LEN;
                aligned = (nbytes_past_boundary == 0);

                if (aligned) {
                        /* if at a packet boundary, write a new TS header */
                        ts_header.continuity_counter = *args->continuity_counter;

                        nbytes += vidtv_memcpy(args->dest_buf,
                                               args->dest_offset + nbytes,
                                               args->dest_buf_sz,
                                               &ts_header,
                                               sizeof(ts_header));
                        /*
                         * This will trigger a discontinuity if the buffer is full,
                         * effectively dropping the packet.
                         */
                        vidtv_ts_inc_cc(args->continuity_counter);
                }

                /* write the pointer_field in the first byte of the payload */
                if (args->new_psi_section)
                        nbytes += vidtv_memset(args->dest_buf,
                                               args->dest_offset + nbytes,
                                               args->dest_buf_sz,
                                               0x0,
                                               1);

                /* write as much of the payload as possible */
                nbytes_past_boundary = (args->dest_offset + nbytes) % TS_PACKET_LEN;
                payload_write_len = min(TS_PACKET_LEN - nbytes_past_boundary, remaining_len);

                nbytes += vidtv_memcpy(args->dest_buf,
                                       args->dest_offset + nbytes,
                                       args->dest_buf_sz,
                                       args->from + payload_offset,
                                       payload_write_len);

                /* 'payload_write_len' written from a total of 'len' requested*/
                remaining_len -= payload_write_len;
                payload_offset += payload_write_len;
        }

        /*
         * fill the rest of the packet if there is any remaining space unused
         */

        nbytes_past_boundary = (args->dest_offset + nbytes) % TS_PACKET_LEN;

        if (args->is_crc)
                nbytes += vidtv_memset(args->dest_buf,
                                       args->dest_offset + nbytes,
                                       args->dest_buf_sz,
                                       TS_FILL_BYTE,
                                       TS_PACKET_LEN - nbytes_past_boundary);

        return nbytes;
}

static u32 table_section_crc32_write_into(struct crc32_write_args *args)
{
        struct psi_write_args psi_args = {
                .dest_buf           = args->dest_buf,
                .from               = &args->crc,
                .len                = CRC_SIZE_IN_BYTES,
                .dest_offset        = args->dest_offset,
                .pid                = args->pid,
                .new_psi_section    = false,
                .continuity_counter = args->continuity_counter,
                .is_crc             = true,
                .dest_buf_sz        = args->dest_buf_sz,
        };

        /* the CRC is the last entry in the section */

        return vidtv_psi_ts_psi_write_into(&psi_args);
}

static void vidtv_psi_desc_chain(struct vidtv_psi_desc *head, struct vidtv_psi_desc *desc)
{
        if (head) {
                while (head->next)
                        head = head->next;

                head->next = desc;
        }
}

struct vidtv_psi_desc_service *vidtv_psi_service_desc_init(struct vidtv_psi_desc *head,
                                                           enum service_type service_type,
                                                           char *service_name,
                                                           char *provider_name)
{
        struct vidtv_psi_desc_service *desc;
        u32 service_name_len = service_name ? strlen(service_name) : 0;
        u32 provider_name_len = provider_name ? strlen(provider_name) : 0;

        desc = kzalloc(sizeof(*desc), GFP_KERNEL);
        if (!desc)
                return NULL;

        desc->type = SERVICE_DESCRIPTOR;

        desc->length = sizeof_field(struct vidtv_psi_desc_service, service_type)
                       + sizeof_field(struct vidtv_psi_desc_service, provider_name_len)
                       + provider_name_len
                       + sizeof_field(struct vidtv_psi_desc_service, service_name_len)
                       + service_name_len;

        desc->service_type = service_type;

        desc->service_name_len = service_name_len;

        if (service_name && service_name_len)
                desc->service_name = kstrdup(service_name, GFP_KERNEL);

        desc->provider_name_len = provider_name_len;

        if (provider_name && provider_name_len)
                desc->provider_name = kstrdup(provider_name, GFP_KERNEL);

        vidtv_psi_desc_chain(head, (struct vidtv_psi_desc *)desc);
        return desc;
}

struct vidtv_psi_desc_registration
*vidtv_psi_registration_desc_init(struct vidtv_psi_desc *head,
                                  __be32 format_id,
                                  u8 *additional_ident_info,
                                  u32 additional_info_len)
{
        struct vidtv_psi_desc_registration *desc;

        desc = kzalloc(sizeof(*desc) + sizeof(format_id) + additional_info_len, GFP_KERNEL);
        if (!desc)
                return NULL;

        desc->type = REGISTRATION_DESCRIPTOR;

        desc->length = sizeof_field(struct vidtv_psi_desc_registration, format_id)
                       + additional_info_len;

        desc->format_id = format_id;

        if (additional_ident_info && additional_info_len)
                memcpy(desc->additional_identification_info,
                       additional_ident_info,
                       additional_info_len);

        vidtv_psi_desc_chain(head, (struct vidtv_psi_desc *)desc);
        return desc;
}

struct vidtv_psi_desc_network_name
*vidtv_psi_network_name_desc_init(struct vidtv_psi_desc *head, char *network_name)
{
        u32 network_name_len = network_name ? strlen(network_name) : 0;
        struct vidtv_psi_desc_network_name *desc;

        desc = kzalloc(sizeof(*desc), GFP_KERNEL);
        if (!desc)
                return NULL;

        desc->type = NETWORK_NAME_DESCRIPTOR;

        desc->length = network_name_len;

        if (network_name && network_name_len)
                desc->network_name = kstrdup(network_name, GFP_KERNEL);

        vidtv_psi_desc_chain(head, (struct vidtv_psi_desc *)desc);
        return desc;
}

struct vidtv_psi_desc_service_list
*vidtv_psi_service_list_desc_init(struct vidtv_psi_desc *head,
                                  struct vidtv_psi_desc_service_list_entry *entry)
{
        struct vidtv_psi_desc_service_list_entry *curr_e = NULL;
        struct vidtv_psi_desc_service_list_entry *head_e = NULL;
        struct vidtv_psi_desc_service_list_entry *prev_e = NULL;
        struct vidtv_psi_desc_service_list *desc;
        u16 length = 0;

        desc = kzalloc(sizeof(*desc), GFP_KERNEL);
        if (!desc)
                return NULL;

        desc->type = SERVICE_LIST_DESCRIPTOR;

        while (entry) {
                curr_e = kzalloc(sizeof(*curr_e), GFP_KERNEL);
                if (!curr_e) {
                        while (head_e) {
                                curr_e = head_e;
                                head_e = head_e->next;
                                kfree(curr_e);
                        }
                        kfree(desc);
                        return NULL;
                }

                curr_e->service_id = entry->service_id;
                curr_e->service_type = entry->service_type;

                length += sizeof(struct vidtv_psi_desc_service_list_entry) -
                          sizeof(struct vidtv_psi_desc_service_list_entry *);

                if (!head_e)
                        head_e = curr_e;
                if (prev_e)
                        prev_e->next = curr_e;

                prev_e = curr_e;
                entry = entry->next;
        }

        desc->length = length;
        desc->service_list = head_e;

        vidtv_psi_desc_chain(head, (struct vidtv_psi_desc *)desc);
        return desc;
}

struct vidtv_psi_desc_short_event
*vidtv_psi_short_event_desc_init(struct vidtv_psi_desc *head,
                                 char *iso_language_code,
                                 char *event_name,
                                 char *text)
{
        u32 iso_len =  iso_language_code ? strlen(iso_language_code) : 0;
        u32 event_name_len = event_name ? strlen(event_name) : 0;
        struct vidtv_psi_desc_short_event *desc;
        u32 text_len =  text ? strlen(text) : 0;

        desc = kzalloc(sizeof(*desc), GFP_KERNEL);
        if (!desc)
                return NULL;

        desc->type = SHORT_EVENT_DESCRIPTOR;

        desc->length = ISO_LANGUAGE_CODE_LEN +
                       sizeof_field(struct vidtv_psi_desc_short_event, event_name_len) +
                       event_name_len +
                       sizeof_field(struct vidtv_psi_desc_short_event, text_len) +
                       text_len;

        desc->event_name_len = event_name_len;
        desc->text_len = text_len;

        if (iso_len != ISO_LANGUAGE_CODE_LEN)
                iso_language_code = "eng";

        desc->iso_language_code = kstrdup(iso_language_code, GFP_KERNEL);

        if (event_name && event_name_len)
                desc->event_name = kstrdup(event_name, GFP_KERNEL);

        if (text && text_len)
                desc->text = kstrdup(text, GFP_KERNEL);

        vidtv_psi_desc_chain(head, (struct vidtv_psi_desc *)desc);
        return desc;
}

struct vidtv_psi_desc *vidtv_psi_desc_clone(struct vidtv_psi_desc *desc)
{
        struct vidtv_psi_desc_network_name *desc_network_name;
        struct vidtv_psi_desc_service_list *desc_service_list;
        struct vidtv_psi_desc_short_event  *desc_short_event;
        struct vidtv_psi_desc_service *service;
        struct vidtv_psi_desc *head = NULL;
        struct vidtv_psi_desc *prev = NULL;
        struct vidtv_psi_desc *curr = NULL;

        while (desc) {
                switch (desc->type) {
                case SERVICE_DESCRIPTOR:
                        service = (struct vidtv_psi_desc_service *)desc;
                        curr = (struct vidtv_psi_desc *)
                               vidtv_psi_service_desc_init(head,
                                                           service->service_type,
                                                           service->service_name,
                                                           service->provider_name);
                break;

                case NETWORK_NAME_DESCRIPTOR:
                        desc_network_name = (struct vidtv_psi_desc_network_name *)desc;
                        curr = (struct vidtv_psi_desc *)
                               vidtv_psi_network_name_desc_init(head,
                                                                desc_network_name->network_name);
                break;

                case SERVICE_LIST_DESCRIPTOR:
                        desc_service_list = (struct vidtv_psi_desc_service_list *)desc;
                        curr = (struct vidtv_psi_desc *)
                               vidtv_psi_service_list_desc_init(head,
                                                                desc_service_list->service_list);
                break;

                case SHORT_EVENT_DESCRIPTOR:
                        desc_short_event = (struct vidtv_psi_desc_short_event *)desc;
                        curr = (struct vidtv_psi_desc *)
                               vidtv_psi_short_event_desc_init(head,
                                                               desc_short_event->iso_language_code,
                                                               desc_short_event->event_name,
                                                               desc_short_event->text);
                break;

                case REGISTRATION_DESCRIPTOR:
                default:
                        curr = kmemdup(desc, sizeof(*desc) + desc->length, GFP_KERNEL);
                        if (!curr)
                                return NULL;
                }

                if (!curr)
                        return NULL;

                curr->next = NULL;
                if (!head)
                        head = curr;
                if (prev)
                        prev->next = curr;

                prev = curr;
                desc = desc->next;
        }

        return head;
}

void vidtv_psi_desc_destroy(struct vidtv_psi_desc *desc)
{
        struct vidtv_psi_desc_service_list_entry *sl_entry_tmp = NULL;
        struct vidtv_psi_desc_service_list_entry *sl_entry = NULL;
        struct vidtv_psi_desc *curr = desc;
        struct vidtv_psi_desc *tmp  = NULL;

        while (curr) {
                tmp  = curr;
                curr = curr->next;

                switch (tmp->type) {
                case SERVICE_DESCRIPTOR:
                        kfree(((struct vidtv_psi_desc_service *)tmp)->provider_name);
                        kfree(((struct vidtv_psi_desc_service *)tmp)->service_name);

                        break;
                case REGISTRATION_DESCRIPTOR:
                        /* nothing to do */
                        break;

                case NETWORK_NAME_DESCRIPTOR:
                        kfree(((struct vidtv_psi_desc_network_name *)tmp)->network_name);
                        break;

                case SERVICE_LIST_DESCRIPTOR:
                        sl_entry = ((struct vidtv_psi_desc_service_list *)tmp)->service_list;
                        while (sl_entry) {
                                sl_entry_tmp = sl_entry;
                                sl_entry = sl_entry->next;
                                kfree(sl_entry_tmp);
                        }
                        break;

                case SHORT_EVENT_DESCRIPTOR:
                        kfree(((struct vidtv_psi_desc_short_event *)tmp)->iso_language_code);
                        kfree(((struct vidtv_psi_desc_short_event *)tmp)->event_name);
                        kfree(((struct vidtv_psi_desc_short_event *)tmp)->text);
                break;

                default:
                        pr_warn_ratelimited("Possible leak: not handling descriptor type %d\n",
                                            tmp->type);
                        break;
                }

                kfree(tmp);
        }
}

static u16
vidtv_psi_desc_comp_loop_len(struct vidtv_psi_desc *desc)
{
        u32 length = 0;

        if (!desc)
                return 0;

        while (desc) {
                length += sizeof_field(struct vidtv_psi_desc, type);
                length += sizeof_field(struct vidtv_psi_desc, length);
                length += desc->length; /* from 'length' field until the end of the descriptor */
                desc    = desc->next;
        }

        return length;
}

void vidtv_psi_desc_assign(struct vidtv_psi_desc **to,
                           struct vidtv_psi_desc *desc)
{
        if (desc == *to)
                return;

        if (*to)
                vidtv_psi_desc_destroy(*to);

        *to = desc;
}

void vidtv_pmt_desc_assign(struct vidtv_psi_table_pmt *pmt,
                           struct vidtv_psi_desc **to,
                           struct vidtv_psi_desc *desc)
{
        vidtv_psi_desc_assign(to, desc);
        vidtv_psi_pmt_table_update_sec_len(pmt);

        if (vidtv_psi_get_sec_len(&pmt->header) > MAX_SECTION_LEN)
                vidtv_psi_desc_assign(to, NULL);

        vidtv_psi_update_version_num(&pmt->header);
}

void vidtv_sdt_desc_assign(struct vidtv_psi_table_sdt *sdt,
                           struct vidtv_psi_desc **to,
                           struct vidtv_psi_desc *desc)
{
        vidtv_psi_desc_assign(to, desc);
        vidtv_psi_sdt_table_update_sec_len(sdt);

        if (vidtv_psi_get_sec_len(&sdt->header) > MAX_SECTION_LEN)
                vidtv_psi_desc_assign(to, NULL);

        vidtv_psi_update_version_num(&sdt->header);
}

static u32 vidtv_psi_desc_write_into(struct desc_write_args *args)
{
        struct psi_write_args psi_args = {
                .dest_buf           = args->dest_buf,
                .from               = &args->desc->type,
                .pid                = args->pid,
                .new_psi_section    = false,
                .continuity_counter = args->continuity_counter,
                .is_crc             = false,
                .dest_buf_sz        = args->dest_buf_sz,
                .crc                = args->crc,
                .len                = sizeof_field(struct vidtv_psi_desc, type) +
                                      sizeof_field(struct vidtv_psi_desc, length),
        };
        struct vidtv_psi_desc_service_list_entry *serv_list_entry = NULL;
        u32 nbytes = 0;

        psi_args.dest_offset        = args->dest_offset + nbytes;

        nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

        switch (args->desc->type) {
        case SERVICE_DESCRIPTOR:
                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = sizeof_field(struct vidtv_psi_desc_service, service_type) +
                               sizeof_field(struct vidtv_psi_desc_service, provider_name_len);
                psi_args.from = &((struct vidtv_psi_desc_service *)args->desc)->service_type;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = ((struct vidtv_psi_desc_service *)args->desc)->provider_name_len;
                psi_args.from = ((struct vidtv_psi_desc_service *)args->desc)->provider_name;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = sizeof_field(struct vidtv_psi_desc_service, service_name_len);
                psi_args.from = &((struct vidtv_psi_desc_service *)args->desc)->service_name_len;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = ((struct vidtv_psi_desc_service *)args->desc)->service_name_len;
                psi_args.from = ((struct vidtv_psi_desc_service *)args->desc)->service_name;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);
                break;

        case NETWORK_NAME_DESCRIPTOR:
                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = args->desc->length;
                psi_args.from = ((struct vidtv_psi_desc_network_name *)args->desc)->network_name;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);
                break;

        case SERVICE_LIST_DESCRIPTOR:
                serv_list_entry = ((struct vidtv_psi_desc_service_list *)args->desc)->service_list;
                while (serv_list_entry) {
                        psi_args.dest_offset = args->dest_offset + nbytes;
                        psi_args.len = sizeof(struct vidtv_psi_desc_service_list_entry) -
                                       sizeof(struct vidtv_psi_desc_service_list_entry *);
                        psi_args.from = serv_list_entry;

                        nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                        serv_list_entry = serv_list_entry->next;
                }
                break;

        case SHORT_EVENT_DESCRIPTOR:
                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = ISO_LANGUAGE_CODE_LEN;
                psi_args.from = ((struct vidtv_psi_desc_short_event *)
                                  args->desc)->iso_language_code;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = sizeof_field(struct vidtv_psi_desc_short_event, event_name_len);
                psi_args.from = &((struct vidtv_psi_desc_short_event *)
                                  args->desc)->event_name_len;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = ((struct vidtv_psi_desc_short_event *)args->desc)->event_name_len;
                psi_args.from = ((struct vidtv_psi_desc_short_event *)args->desc)->event_name;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = sizeof_field(struct vidtv_psi_desc_short_event, text_len);
                psi_args.from = &((struct vidtv_psi_desc_short_event *)args->desc)->text_len;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = ((struct vidtv_psi_desc_short_event *)args->desc)->text_len;
                psi_args.from = ((struct vidtv_psi_desc_short_event *)args->desc)->text;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                break;

        case REGISTRATION_DESCRIPTOR:
        default:
                psi_args.dest_offset = args->dest_offset + nbytes;
                psi_args.len = args->desc->length;
                psi_args.from = &args->desc->data;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);
                break;
        }

        return nbytes;
}

static u32
vidtv_psi_table_header_write_into(struct header_write_args *args)
{
        struct psi_write_args psi_args = {
                .dest_buf           = args->dest_buf,
                .from               = args->h,
                .len                = sizeof(struct vidtv_psi_table_header),
                .dest_offset        = args->dest_offset,
                .pid                = args->pid,
                .new_psi_section    = true,
                .continuity_counter = args->continuity_counter,
                .is_crc             = false,
                .dest_buf_sz        = args->dest_buf_sz,
                .crc                = args->crc,
        };

        return vidtv_psi_ts_psi_write_into(&psi_args);
}

void
vidtv_psi_pat_table_update_sec_len(struct vidtv_psi_table_pat *pat)
{
        u16 length = 0;
        u32 i;

        /* see ISO/IEC 13818-1 : 2000 p.43 */

        /* from immediately after 'section_length' until 'last_section_number'*/
        length += PAT_LEN_UNTIL_LAST_SECTION_NUMBER;

        /* do not count the pointer */
        for (i = 0; i < pat->num_pat; ++i)
                length += sizeof(struct vidtv_psi_table_pat_program) -
                          sizeof(struct vidtv_psi_table_pat_program *);

        length += CRC_SIZE_IN_BYTES;

        vidtv_psi_set_sec_len(&pat->header, length);
}

void vidtv_psi_pmt_table_update_sec_len(struct vidtv_psi_table_pmt *pmt)
{
        struct vidtv_psi_table_pmt_stream *s = pmt->stream;
        u16 desc_loop_len;
        u16 length = 0;

        /* see ISO/IEC 13818-1 : 2000 p.46 */

        /* from immediately after 'section_length' until 'program_info_length'*/
        length += PMT_LEN_UNTIL_PROGRAM_INFO_LENGTH;

        desc_loop_len = vidtv_psi_desc_comp_loop_len(pmt->descriptor);
        vidtv_psi_set_desc_loop_len(&pmt->bitfield2, desc_loop_len, 10);

        length += desc_loop_len;

        while (s) {
                /* skip both pointers at the end */
                length += sizeof(struct vidtv_psi_table_pmt_stream) -
                          sizeof(struct vidtv_psi_desc *) -
                          sizeof(struct vidtv_psi_table_pmt_stream *);

                desc_loop_len = vidtv_psi_desc_comp_loop_len(s->descriptor);
                vidtv_psi_set_desc_loop_len(&s->bitfield2, desc_loop_len, 10);

                length += desc_loop_len;

                s = s->next;
        }

        length += CRC_SIZE_IN_BYTES;

        vidtv_psi_set_sec_len(&pmt->header, length);
}

void vidtv_psi_sdt_table_update_sec_len(struct vidtv_psi_table_sdt *sdt)
{
        struct vidtv_psi_table_sdt_service *s = sdt->service;
        u16 desc_loop_len;
        u16 length = 0;

        /* see ETSI EN 300 468 V 1.10.1 p.24 */

        /*
         * from immediately after 'section_length' until
         * 'reserved_for_future_use'
         */
        length += SDT_LEN_UNTIL_RESERVED_FOR_FUTURE_USE;

        while (s) {
                /* skip both pointers at the end */
                length += sizeof(struct vidtv_psi_table_sdt_service) -
                          sizeof(struct vidtv_psi_desc *) -
                          sizeof(struct vidtv_psi_table_sdt_service *);

                desc_loop_len = vidtv_psi_desc_comp_loop_len(s->descriptor);
                vidtv_psi_set_desc_loop_len(&s->bitfield, desc_loop_len, 12);

                length += desc_loop_len;

                s = s->next;
        }

        length += CRC_SIZE_IN_BYTES;
        vidtv_psi_set_sec_len(&sdt->header, length);
}

struct vidtv_psi_table_pat_program*
vidtv_psi_pat_program_init(struct vidtv_psi_table_pat_program *head,
                           u16 service_id,
                           u16 program_map_pid)
{
        struct vidtv_psi_table_pat_program *program;
        const u16 RESERVED = 0x07;

        program = kzalloc(sizeof(*program), GFP_KERNEL);
        if (!program)
                return NULL;

        program->service_id = cpu_to_be16(service_id);

        /* pid for the PMT section in the TS */
        program->bitfield = cpu_to_be16((RESERVED << 13) | program_map_pid);
        program->next = NULL;

        if (head) {
                while (head->next)
                        head = head->next;

                head->next = program;
        }

        return program;
}

void
vidtv_psi_pat_program_destroy(struct vidtv_psi_table_pat_program *p)
{
        struct vidtv_psi_table_pat_program *tmp  = NULL;
        struct vidtv_psi_table_pat_program *curr = p;

        while (curr) {
                tmp  = curr;
                curr = curr->next;
                kfree(tmp);
        }
}

/* This function transfers ownership of p to the table */
void
vidtv_psi_pat_program_assign(struct vidtv_psi_table_pat *pat,
                             struct vidtv_psi_table_pat_program *p)
{
        struct vidtv_psi_table_pat_program *program;
        u16 program_count;

        do {
                program_count = 0;
                program = p;

                if (p == pat->program)
                        return;

                while (program) {
                        ++program_count;
                        program = program->next;
                }

                pat->num_pat = program_count;
                pat->program  = p;

                /* Recompute section length */
                vidtv_psi_pat_table_update_sec_len(pat);

                p = NULL;
        } while (vidtv_psi_get_sec_len(&pat->header) > MAX_SECTION_LEN);

        vidtv_psi_update_version_num(&pat->header);
}

struct vidtv_psi_table_pat *vidtv_psi_pat_table_init(u16 transport_stream_id)
{
        struct vidtv_psi_table_pat *pat;
        const u16 SYNTAX = 0x1;
        const u16 ZERO = 0x0;
        const u16 ONES = 0x03;

        pat = kzalloc(sizeof(*pat), GFP_KERNEL);
        if (!pat)
                return NULL;

        pat->header.table_id = 0x0;

        pat->header.bitfield = cpu_to_be16((SYNTAX << 15) | (ZERO << 14) | (ONES << 12));
        pat->header.id           = cpu_to_be16(transport_stream_id);
        pat->header.current_next = 0x1;

        pat->header.version = 0x1f;

        pat->header.one2         = 0x03;
        pat->header.section_id   = 0x0;
        pat->header.last_section = 0x0;

        vidtv_psi_pat_table_update_sec_len(pat);

        return pat;
}

u32 vidtv_psi_pat_write_into(struct vidtv_psi_pat_write_args *args)
{
        struct vidtv_psi_table_pat_program *p = args->pat->program;
        struct header_write_args h_args       = {
                .dest_buf           = args->buf,
                .dest_offset        = args->offset,
                .pid                = VIDTV_PAT_PID,
                .h                  = &args->pat->header,
                .continuity_counter = args->continuity_counter,
                .dest_buf_sz        = args->buf_sz,
        };
        struct psi_write_args psi_args        = {
                .dest_buf           = args->buf,
                .pid                = VIDTV_PAT_PID,
                .new_psi_section    = false,
                .continuity_counter = args->continuity_counter,
                .is_crc             = false,
                .dest_buf_sz        = args->buf_sz,
        };
        struct crc32_write_args c_args        = {
                .dest_buf           = args->buf,
                .pid                = VIDTV_PAT_PID,
                .dest_buf_sz        = args->buf_sz,
        };
        u32 crc = INITIAL_CRC;
        u32 nbytes = 0;

        vidtv_psi_pat_table_update_sec_len(args->pat);

        h_args.crc = &crc;

        nbytes += vidtv_psi_table_header_write_into(&h_args);

        /* note that the field 'u16 programs' is not really part of the PAT */

        psi_args.crc = &crc;

        while (p) {
                /* copy the PAT programs */

                psi_args.from = p;
                /* skip the pointer */
                psi_args.len = sizeof(*p) -
                               sizeof(struct vidtv_psi_table_pat_program *);
                psi_args.dest_offset = args->offset + nbytes;
                psi_args.continuity_counter = args->continuity_counter;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                p = p->next;
        }

        c_args.dest_offset        = args->offset + nbytes;
        c_args.continuity_counter = args->continuity_counter;
        c_args.crc                = cpu_to_be32(crc);

        /* Write the CRC32 at the end */
        nbytes += table_section_crc32_write_into(&c_args);

        return nbytes;
}

void
vidtv_psi_pat_table_destroy(struct vidtv_psi_table_pat *p)
{
        vidtv_psi_pat_program_destroy(p->program);
        kfree(p);
}

struct vidtv_psi_table_pmt_stream*
vidtv_psi_pmt_stream_init(struct vidtv_psi_table_pmt_stream *head,
                          enum vidtv_psi_stream_types stream_type,
                          u16 es_pid)
{
        struct vidtv_psi_table_pmt_stream *stream;
        const u16 RESERVED1 = 0x07;
        const u16 RESERVED2 = 0x0f;
        const u16 ZERO = 0x0;
        u16 desc_loop_len;

        stream = kzalloc(sizeof(*stream), GFP_KERNEL);
        if (!stream)
                return NULL;

        stream->type = stream_type;

        stream->bitfield = cpu_to_be16((RESERVED1 << 13) | es_pid);

        desc_loop_len = vidtv_psi_desc_comp_loop_len(stream->descriptor);

        stream->bitfield2 = cpu_to_be16((RESERVED2 << 12) |
                                        (ZERO << 10)      |
                                        desc_loop_len);
        stream->next = NULL;

        if (head) {
                while (head->next)
                        head = head->next;

                head->next = stream;
        }

        return stream;
}

void vidtv_psi_pmt_stream_destroy(struct vidtv_psi_table_pmt_stream *s)
{
        struct vidtv_psi_table_pmt_stream *tmp_stream  = NULL;
        struct vidtv_psi_table_pmt_stream *curr_stream = s;

        while (curr_stream) {
                tmp_stream  = curr_stream;
                curr_stream = curr_stream->next;
                vidtv_psi_desc_destroy(tmp_stream->descriptor);
                kfree(tmp_stream);
        }
}

void vidtv_psi_pmt_stream_assign(struct vidtv_psi_table_pmt *pmt,
                                 struct vidtv_psi_table_pmt_stream *s)
{
        do {
                /* This function transfers ownership of s to the table */
                if (s == pmt->stream)
                        return;

                pmt->stream = s;
                vidtv_psi_pmt_table_update_sec_len(pmt);

                s = NULL;
        } while (vidtv_psi_get_sec_len(&pmt->header) > MAX_SECTION_LEN);

        vidtv_psi_update_version_num(&pmt->header);
}

u16 vidtv_psi_pmt_get_pid(struct vidtv_psi_table_pmt *section,
                          struct vidtv_psi_table_pat *pat)
{
        struct vidtv_psi_table_pat_program *program = pat->program;

        /*
         * service_id is the same as program_number in the
         * corresponding program_map_section
         * see ETSI EN 300 468 v1.15.1 p. 24
         */
        while (program) {
                if (program->service_id == section->header.id)
                        return vidtv_psi_get_pat_program_pid(program);

                program = program->next;
        }

        return TS_LAST_VALID_PID + 1; /* not found */
}

struct vidtv_psi_table_pmt *vidtv_psi_pmt_table_init(u16 program_number,
                                                     u16 pcr_pid)
{
        struct vidtv_psi_table_pmt *pmt;
        const u16 RESERVED1 = 0x07;
        const u16 RESERVED2 = 0x0f;
        const u16 SYNTAX = 0x1;
        const u16 ONES = 0x03;
        const u16 ZERO = 0x0;
        u16 desc_loop_len;

        pmt = kzalloc(sizeof(*pmt), GFP_KERNEL);
        if (!pmt)
                return NULL;

        if (!pcr_pid)
                pcr_pid = 0x1fff;

        pmt->header.table_id = 0x2;

        pmt->header.bitfield = cpu_to_be16((SYNTAX << 15) | (ZERO << 14) | (ONES << 12));

        pmt->header.id = cpu_to_be16(program_number);
        pmt->header.current_next = 0x1;

        pmt->header.version = 0x1f;

        pmt->header.one2 = ONES;
        pmt->header.section_id   = 0;
        pmt->header.last_section = 0;

        pmt->bitfield = cpu_to_be16((RESERVED1 << 13) | pcr_pid);

        desc_loop_len = vidtv_psi_desc_comp_loop_len(pmt->descriptor);

        pmt->bitfield2 = cpu_to_be16((RESERVED2 << 12) |
                                     (ZERO << 10)      |
                                     desc_loop_len);

        vidtv_psi_pmt_table_update_sec_len(pmt);

        return pmt;
}

u32 vidtv_psi_pmt_write_into(struct vidtv_psi_pmt_write_args *args)
{
        struct vidtv_psi_desc *table_descriptor   = args->pmt->descriptor;
        struct vidtv_psi_table_pmt_stream *stream = args->pmt->stream;
        struct vidtv_psi_desc *stream_descriptor;
        u32 crc = INITIAL_CRC;
        u32 nbytes = 0;
        struct header_write_args h_args = {
                .dest_buf           = args->buf,
                .dest_offset        = args->offset,
                .h                  = &args->pmt->header,
                .pid                = args->pid,
                .continuity_counter = args->continuity_counter,
                .dest_buf_sz        = args->buf_sz,
        };
        struct psi_write_args psi_args  = {
                .dest_buf = args->buf,
                .from     = &args->pmt->bitfield,
                .len      = sizeof_field(struct vidtv_psi_table_pmt, bitfield) +
                            sizeof_field(struct vidtv_psi_table_pmt, bitfield2),
                .pid                = args->pid,
                .new_psi_section    = false,
                .is_crc             = false,
                .dest_buf_sz        = args->buf_sz,
                .crc                = &crc,
        };
        struct desc_write_args d_args   = {
                .dest_buf           = args->buf,
                .desc               = table_descriptor,
                .pid                = args->pid,
                .dest_buf_sz        = args->buf_sz,
        };
        struct crc32_write_args c_args  = {
                .dest_buf           = args->buf,
                .pid                = args->pid,
                .dest_buf_sz        = args->buf_sz,
        };

        vidtv_psi_pmt_table_update_sec_len(args->pmt);

        h_args.crc                = &crc;

        nbytes += vidtv_psi_table_header_write_into(&h_args);

        /* write the two bitfields */
        psi_args.dest_offset        = args->offset + nbytes;
        psi_args.continuity_counter = args->continuity_counter;
        nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

        while (table_descriptor) {
                /* write the descriptors, if any */
                d_args.dest_offset        = args->offset + nbytes;
                d_args.continuity_counter = args->continuity_counter;
                d_args.crc                = &crc;

                nbytes += vidtv_psi_desc_write_into(&d_args);

                table_descriptor = table_descriptor->next;
        }

        psi_args.len += sizeof_field(struct vidtv_psi_table_pmt_stream, type);
        while (stream) {
                /* write the streams, if any */
                psi_args.from = stream;
                psi_args.dest_offset = args->offset + nbytes;
                psi_args.continuity_counter = args->continuity_counter;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                stream_descriptor = stream->descriptor;

                while (stream_descriptor) {
                        /* write the stream descriptors, if any */
                        d_args.dest_offset        = args->offset + nbytes;
                        d_args.desc               = stream_descriptor;
                        d_args.continuity_counter = args->continuity_counter;
                        d_args.crc                = &crc;

                        nbytes += vidtv_psi_desc_write_into(&d_args);

                        stream_descriptor = stream_descriptor->next;
                }

                stream = stream->next;
        }

        c_args.dest_offset        = args->offset + nbytes;
        c_args.crc                = cpu_to_be32(crc);
        c_args.continuity_counter = args->continuity_counter;

        /* Write the CRC32 at the end */
        nbytes += table_section_crc32_write_into(&c_args);

        return nbytes;
}

void vidtv_psi_pmt_table_destroy(struct vidtv_psi_table_pmt *pmt)
{
        vidtv_psi_desc_destroy(pmt->descriptor);
        vidtv_psi_pmt_stream_destroy(pmt->stream);
        kfree(pmt);
}

struct vidtv_psi_table_sdt *vidtv_psi_sdt_table_init(u16 network_id,
                                                     u16 transport_stream_id)
{
        struct vidtv_psi_table_sdt *sdt;
        const u16 RESERVED = 0xff;
        const u16 SYNTAX = 0x1;
        const u16 ONES = 0x03;
        const u16 ONE = 0x1;

        sdt  = kzalloc(sizeof(*sdt), GFP_KERNEL);
        if (!sdt)
                return NULL;

        sdt->header.table_id = 0x42;
        sdt->header.bitfield = cpu_to_be16((SYNTAX << 15) | (ONE << 14) | (ONES << 12));

        /*
         * This is a 16-bit field which serves as a label for identification
         * of the TS, about which the SDT informs, from any other multiplex
         * within the delivery system.
         */
        sdt->header.id = cpu_to_be16(transport_stream_id);
        sdt->header.current_next = ONE;

        sdt->header.version = 0x1f;

        sdt->header.one2  = ONES;
        sdt->header.section_id   = 0;
        sdt->header.last_section = 0;

        /*
         * FIXME: The network_id range from 0xFF01 to 0xFFFF is used to
         * indicate temporary private use. For now, let's use the first
         * value.
         * This can be changed to something more useful, when support for
         * NIT gets added
         */
        sdt->network_id = cpu_to_be16(network_id);
        sdt->reserved = RESERVED;

        vidtv_psi_sdt_table_update_sec_len(sdt);

        return sdt;
}

u32 vidtv_psi_sdt_write_into(struct vidtv_psi_sdt_write_args *args)
{
        struct header_write_args h_args = {
                .dest_buf           = args->buf,
                .dest_offset        = args->offset,
                .h                  = &args->sdt->header,
                .pid                = VIDTV_SDT_PID,
                .dest_buf_sz        = args->buf_sz,
        };
        struct psi_write_args psi_args  = {
                .dest_buf = args->buf,
                .len = sizeof_field(struct vidtv_psi_table_sdt, network_id) +
                       sizeof_field(struct vidtv_psi_table_sdt, reserved),
                .pid                = VIDTV_SDT_PID,
                .new_psi_section    = false,
                .is_crc             = false,
                .dest_buf_sz        = args->buf_sz,
        };
        struct desc_write_args d_args   = {
                .dest_buf           = args->buf,
                .pid                = VIDTV_SDT_PID,
                .dest_buf_sz        = args->buf_sz,
        };
        struct crc32_write_args c_args  = {
                .dest_buf           = args->buf,
                .pid                = VIDTV_SDT_PID,
                .dest_buf_sz        = args->buf_sz,
        };
        struct vidtv_psi_table_sdt_service *service = args->sdt->service;
        struct vidtv_psi_desc *service_desc;
        u32 nbytes  = 0;
        u32 crc = INITIAL_CRC;

        /* see ETSI EN 300 468 v1.15.1 p. 11 */

        vidtv_psi_sdt_table_update_sec_len(args->sdt);

        h_args.continuity_counter = args->continuity_counter;
        h_args.crc                = &crc;

        nbytes += vidtv_psi_table_header_write_into(&h_args);

        psi_args.from               = &args->sdt->network_id;
        psi_args.dest_offset        = args->offset + nbytes;
        psi_args.continuity_counter = args->continuity_counter;
        psi_args.crc                = &crc;

        /* copy u16 network_id + u8 reserved)*/
        nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

        /* skip both pointers at the end */
        psi_args.len = sizeof(struct vidtv_psi_table_sdt_service) -
                       sizeof(struct vidtv_psi_desc *) -
                       sizeof(struct vidtv_psi_table_sdt_service *);

        while (service) {
                /* copy the services, if any */
                psi_args.from = service;
                psi_args.dest_offset = args->offset + nbytes;
                psi_args.continuity_counter = args->continuity_counter;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                service_desc = service->descriptor;

                while (service_desc) {
                        /* copy the service descriptors, if any */
                        d_args.dest_offset        = args->offset + nbytes;
                        d_args.desc               = service_desc;
                        d_args.continuity_counter = args->continuity_counter;
                        d_args.crc                = &crc;

                        nbytes += vidtv_psi_desc_write_into(&d_args);

                        service_desc = service_desc->next;
                }

                service = service->next;
        }

        c_args.dest_offset        = args->offset + nbytes;
        c_args.crc                = cpu_to_be32(crc);
        c_args.continuity_counter = args->continuity_counter;

        /* Write the CRC at the end */
        nbytes += table_section_crc32_write_into(&c_args);

        return nbytes;
}

void vidtv_psi_sdt_table_destroy(struct vidtv_psi_table_sdt *sdt)
{
        vidtv_psi_sdt_service_destroy(sdt->service);
        kfree(sdt);
}

struct vidtv_psi_table_sdt_service
*vidtv_psi_sdt_service_init(struct vidtv_psi_table_sdt_service *head,
                            u16 service_id,
                            bool eit_schedule,
                            bool eit_present_following)
{
        struct vidtv_psi_table_sdt_service *service;

        service = kzalloc(sizeof(*service), GFP_KERNEL);
        if (!service)
                return NULL;

        /*
         * ETSI 300 468: this is a 16bit field which serves as a label to
         * identify this service from any other service within the TS.
         * The service id is the same as the program number in the
         * corresponding program_map_section
         */
        service->service_id            = cpu_to_be16(service_id);
        service->EIT_schedule          = eit_schedule;
        service->EIT_present_following = eit_present_following;
        service->reserved              = 0x3f;

        service->bitfield = cpu_to_be16(RUNNING << 13);

        if (head) {
                while (head->next)
                        head = head->next;

                head->next = service;
        }

        return service;
}

void
vidtv_psi_sdt_service_destroy(struct vidtv_psi_table_sdt_service *service)
{
        struct vidtv_psi_table_sdt_service *curr = service;
        struct vidtv_psi_table_sdt_service *tmp  = NULL;

        while (curr) {
                tmp  = curr;
                curr = curr->next;
                vidtv_psi_desc_destroy(tmp->descriptor);
                kfree(tmp);
        }
}

void
vidtv_psi_sdt_service_assign(struct vidtv_psi_table_sdt *sdt,
                             struct vidtv_psi_table_sdt_service *service)
{
        do {
                if (service == sdt->service)
                        return;

                sdt->service = service;

                /* recompute section length */
                vidtv_psi_sdt_table_update_sec_len(sdt);

                service = NULL;
        } while (vidtv_psi_get_sec_len(&sdt->header) > MAX_SECTION_LEN);

        vidtv_psi_update_version_num(&sdt->header);
}

/*
 * PMTs contain information about programs. For each program,
 * there is one PMT section. This function will create a section
 * for each program found in the PAT
 */
struct vidtv_psi_table_pmt**
vidtv_psi_pmt_create_sec_for_each_pat_entry(struct vidtv_psi_table_pat *pat,
                                            u16 pcr_pid)

{
        struct vidtv_psi_table_pat_program *program;
        struct vidtv_psi_table_pmt **pmt_secs;
        u32 i = 0, num_pmt = 0;

        /*
         * The number of PMT entries is the number of PAT entries
         * that contain service_id. That exclude special tables, like NIT
         */
        program = pat->program;
        while (program) {
                if (program->service_id)
                        num_pmt++;
                program = program->next;
        }

        pmt_secs = kcalloc(num_pmt,
                           sizeof(struct vidtv_psi_table_pmt *),
                           GFP_KERNEL);
        if (!pmt_secs)
                return NULL;

        for (program = pat->program; program; program = program->next) {
                if (!program->service_id)
                        continue;
                pmt_secs[i] = vidtv_psi_pmt_table_init(be16_to_cpu(program->service_id),
                                                       pcr_pid);

                if (!pmt_secs[i]) {
                        while (i > 0) {
                                i--;
                                vidtv_psi_pmt_table_destroy(pmt_secs[i]);
                        }
                        return NULL;
                }
                i++;
        }
        pat->num_pmt = num_pmt;

        return pmt_secs;
}

/* find the PMT section associated with 'program_num' */
struct vidtv_psi_table_pmt
*vidtv_psi_find_pmt_sec(struct vidtv_psi_table_pmt **pmt_sections,
                        u16 nsections,
                        u16 program_num)
{
        struct vidtv_psi_table_pmt *sec = NULL;
        u32 i;

        for (i = 0; i < nsections; ++i) {
                sec = pmt_sections[i];
                if (be16_to_cpu(sec->header.id) == program_num)
                        return sec;
        }

        return NULL; /* not found */
}

static void vidtv_psi_nit_table_update_sec_len(struct vidtv_psi_table_nit *nit)
{
        u16 length = 0;
        struct vidtv_psi_table_transport *t = nit->transport;
        u16 desc_loop_len;
        u16 transport_loop_len = 0;

        /*
         * from immediately after 'section_length' until
         * 'network_descriptor_length'
         */
        length += NIT_LEN_UNTIL_NETWORK_DESCRIPTOR_LEN;

        desc_loop_len = vidtv_psi_desc_comp_loop_len(nit->descriptor);
        vidtv_psi_set_desc_loop_len(&nit->bitfield, desc_loop_len, 12);

        length += desc_loop_len;

        length += sizeof_field(struct vidtv_psi_table_nit, bitfield2);

        while (t) {
                /* skip both pointers at the end */
                transport_loop_len += sizeof(struct vidtv_psi_table_transport) -
                                      sizeof(struct vidtv_psi_desc *) -
                                      sizeof(struct vidtv_psi_table_transport *);

                length += transport_loop_len;

                desc_loop_len = vidtv_psi_desc_comp_loop_len(t->descriptor);
                vidtv_psi_set_desc_loop_len(&t->bitfield, desc_loop_len, 12);

                length += desc_loop_len;

                t = t->next;
        }

        // Actually sets the transport stream loop len, maybe rename this function later
        vidtv_psi_set_desc_loop_len(&nit->bitfield2, transport_loop_len, 12);
        length += CRC_SIZE_IN_BYTES;

        vidtv_psi_set_sec_len(&nit->header, length);
}

struct vidtv_psi_table_nit
*vidtv_psi_nit_table_init(u16 network_id,
                          u16 transport_stream_id,
                          char *network_name,
                          struct vidtv_psi_desc_service_list_entry *service_list)
{
        struct vidtv_psi_table_transport *transport;
        struct vidtv_psi_table_nit *nit;
        const u16 SYNTAX = 0x1;
        const u16 ONES = 0x03;
        const u16 ONE = 0x1;

        nit = kzalloc(sizeof(*nit), GFP_KERNEL);
        if (!nit)
                return NULL;

        transport = kzalloc(sizeof(*transport), GFP_KERNEL);
        if (!transport)
                goto free_nit;

        nit->header.table_id = 0x40; // ACTUAL_NETWORK

        nit->header.bitfield = cpu_to_be16((SYNTAX << 15) | (ONE << 14) | (ONES << 12));

        nit->header.id = cpu_to_be16(network_id);
        nit->header.current_next = ONE;

        nit->header.version = 0x1f;

        nit->header.one2  = ONES;
        nit->header.section_id   = 0;
        nit->header.last_section = 0;

        nit->bitfield = cpu_to_be16(0xf);
        nit->bitfield2 = cpu_to_be16(0xf);

        nit->descriptor = (struct vidtv_psi_desc *)
                          vidtv_psi_network_name_desc_init(NULL, network_name);
        if (!nit->descriptor)
                goto free_transport;

        transport->transport_id = cpu_to_be16(transport_stream_id);
        transport->network_id = cpu_to_be16(network_id);
        transport->bitfield = cpu_to_be16(0xf);
        transport->descriptor = (struct vidtv_psi_desc *)
                                vidtv_psi_service_list_desc_init(NULL, service_list);
        if (!transport->descriptor)
                goto free_nit_desc;

        nit->transport = transport;

        vidtv_psi_nit_table_update_sec_len(nit);

        return nit;

free_nit_desc:
        vidtv_psi_desc_destroy((struct vidtv_psi_desc *)nit->descriptor);

free_transport:
        kfree(transport);
free_nit:
        kfree(nit);
        return NULL;
}

u32 vidtv_psi_nit_write_into(struct vidtv_psi_nit_write_args *args)
{
        struct header_write_args h_args = {
                .dest_buf           = args->buf,
                .dest_offset        = args->offset,
                .h                  = &args->nit->header,
                .pid                = VIDTV_NIT_PID,
                .dest_buf_sz        = args->buf_sz,
        };
        struct psi_write_args psi_args  = {
                .dest_buf           = args->buf,
                .from               = &args->nit->bitfield,
                .len                = sizeof_field(struct vidtv_psi_table_nit, bitfield),
                .pid                = VIDTV_NIT_PID,
                .new_psi_section    = false,
                .is_crc             = false,
                .dest_buf_sz        = args->buf_sz,
        };
        struct desc_write_args d_args   = {
                .dest_buf           = args->buf,
                .pid                = VIDTV_NIT_PID,
                .dest_buf_sz        = args->buf_sz,
        };
        struct crc32_write_args c_args  = {
                .dest_buf           = args->buf,
                .pid                = VIDTV_NIT_PID,
                .dest_buf_sz        = args->buf_sz,
        };
        struct vidtv_psi_desc *table_descriptor     = args->nit->descriptor;
        struct vidtv_psi_table_transport *transport = args->nit->transport;
        struct vidtv_psi_desc *transport_descriptor;
        u32 crc = INITIAL_CRC;
        u32 nbytes = 0;

        vidtv_psi_nit_table_update_sec_len(args->nit);

        h_args.continuity_counter = args->continuity_counter;
        h_args.crc                = &crc;

        nbytes += vidtv_psi_table_header_write_into(&h_args);

        /* write the bitfield */

        psi_args.dest_offset        = args->offset + nbytes;
        psi_args.continuity_counter = args->continuity_counter;
        psi_args.crc                = &crc;

        nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

        while (table_descriptor) {
                /* write the descriptors, if any */
                d_args.dest_offset        = args->offset + nbytes;
                d_args.desc               = table_descriptor;
                d_args.continuity_counter = args->continuity_counter;
                d_args.crc                = &crc;

                nbytes += vidtv_psi_desc_write_into(&d_args);

                table_descriptor = table_descriptor->next;
        }

        /* write the second bitfield */
        psi_args.from = &args->nit->bitfield2;
        psi_args.len = sizeof_field(struct vidtv_psi_table_nit, bitfield2);
        psi_args.dest_offset = args->offset + nbytes;

        nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

        psi_args.len  = sizeof_field(struct vidtv_psi_table_transport, transport_id) +
                        sizeof_field(struct vidtv_psi_table_transport, network_id)   +
                        sizeof_field(struct vidtv_psi_table_transport, bitfield);
        while (transport) {
                /* write the transport sections, if any */
                psi_args.from = transport;
                psi_args.dest_offset = args->offset + nbytes;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                transport_descriptor = transport->descriptor;

                while (transport_descriptor) {
                        /* write the transport descriptors, if any */
                        d_args.dest_offset        = args->offset + nbytes;
                        d_args.desc               = transport_descriptor;
                        d_args.continuity_counter = args->continuity_counter;
                        d_args.crc                = &crc;

                        nbytes += vidtv_psi_desc_write_into(&d_args);

                        transport_descriptor = transport_descriptor->next;
                }

                transport = transport->next;
        }

        c_args.dest_offset        = args->offset + nbytes;
        c_args.crc                = cpu_to_be32(crc);
        c_args.continuity_counter = args->continuity_counter;

        /* Write the CRC32 at the end */
        nbytes += table_section_crc32_write_into(&c_args);

        return nbytes;
}

static void vidtv_psi_transport_destroy(struct vidtv_psi_table_transport *t)
{
        struct vidtv_psi_table_transport *tmp_t  = NULL;
        struct vidtv_psi_table_transport *curr_t = t;

        while (curr_t) {
                tmp_t  = curr_t;
                curr_t = curr_t->next;
                vidtv_psi_desc_destroy(tmp_t->descriptor);
                kfree(tmp_t);
        }
}

void vidtv_psi_nit_table_destroy(struct vidtv_psi_table_nit *nit)
{
        vidtv_psi_desc_destroy(nit->descriptor);
        vidtv_psi_transport_destroy(nit->transport);
        kfree(nit);
}

void vidtv_psi_eit_table_update_sec_len(struct vidtv_psi_table_eit *eit)
{
        struct vidtv_psi_table_eit_event *e = eit->event;
        u16 desc_loop_len;
        u16 length = 0;

        /*
         * from immediately after 'section_length' until
         * 'last_table_id'
         */
        length += EIT_LEN_UNTIL_LAST_TABLE_ID;

        while (e) {
                /* skip both pointers at the end */
                length += sizeof(struct vidtv_psi_table_eit_event) -
                          sizeof(struct vidtv_psi_desc *) -
                          sizeof(struct vidtv_psi_table_eit_event *);

                desc_loop_len = vidtv_psi_desc_comp_loop_len(e->descriptor);
                vidtv_psi_set_desc_loop_len(&e->bitfield, desc_loop_len, 12);

                length += desc_loop_len;

                e = e->next;
        }

        length += CRC_SIZE_IN_BYTES;

        vidtv_psi_set_sec_len(&eit->header, length);
}

void vidtv_psi_eit_event_assign(struct vidtv_psi_table_eit *eit,
                                struct vidtv_psi_table_eit_event *e)
{
        do {
                if (e == eit->event)
                        return;

                eit->event = e;
                vidtv_psi_eit_table_update_sec_len(eit);

                e = NULL;
        } while (vidtv_psi_get_sec_len(&eit->header) > EIT_MAX_SECTION_LEN);

        vidtv_psi_update_version_num(&eit->header);
}

struct vidtv_psi_table_eit
*vidtv_psi_eit_table_init(u16 network_id,
                          u16 transport_stream_id,
                          __be16 service_id)
{
        struct vidtv_psi_table_eit *eit;
        const u16 SYNTAX = 0x1;
        const u16 ONE = 0x1;
        const u16 ONES = 0x03;

        eit = kzalloc(sizeof(*eit), GFP_KERNEL);
        if (!eit)
                return NULL;

        eit->header.table_id = 0x4e; //actual_transport_stream: present/following

        eit->header.bitfield = cpu_to_be16((SYNTAX << 15) | (ONE << 14) | (ONES << 12));

        eit->header.id = service_id;
        eit->header.current_next = ONE;

        eit->header.version = 0x1f;

        eit->header.one2  = ONES;
        eit->header.section_id   = 0;
        eit->header.last_section = 0;

        eit->transport_id = cpu_to_be16(transport_stream_id);
        eit->network_id = cpu_to_be16(network_id);

        eit->last_segment = eit->header.last_section; /* not implemented */
        eit->last_table_id = eit->header.table_id; /* not implemented */

        vidtv_psi_eit_table_update_sec_len(eit);

        return eit;
}

u32 vidtv_psi_eit_write_into(struct vidtv_psi_eit_write_args *args)
{
        struct header_write_args h_args = {
                .dest_buf        = args->buf,
                .dest_offset     = args->offset,
                .h               = &args->eit->header,
                .pid             = VIDTV_EIT_PID,
                .dest_buf_sz     = args->buf_sz,
        };
        struct psi_write_args psi_args  = {
                .dest_buf        = args->buf,
                .len             = sizeof_field(struct vidtv_psi_table_eit, transport_id) +
                                   sizeof_field(struct vidtv_psi_table_eit, network_id)   +
                                   sizeof_field(struct vidtv_psi_table_eit, last_segment) +
                                   sizeof_field(struct vidtv_psi_table_eit, last_table_id),
                .pid             = VIDTV_EIT_PID,
                .new_psi_section = false,
                .is_crc          = false,
                .dest_buf_sz     = args->buf_sz,
        };
        struct desc_write_args d_args   = {
                .dest_buf           = args->buf,
                .pid                = VIDTV_EIT_PID,
                .dest_buf_sz        = args->buf_sz,
        };
        struct crc32_write_args c_args  = {
                .dest_buf           = args->buf,
                .pid                = VIDTV_EIT_PID,
                .dest_buf_sz        = args->buf_sz,
        };
        struct vidtv_psi_table_eit_event *event = args->eit->event;
        struct vidtv_psi_desc *event_descriptor;
        u32 crc = INITIAL_CRC;
        u32 nbytes  = 0;

        vidtv_psi_eit_table_update_sec_len(args->eit);

        h_args.continuity_counter = args->continuity_counter;
        h_args.crc                = &crc;

        nbytes += vidtv_psi_table_header_write_into(&h_args);

        psi_args.from               = &args->eit->transport_id;
        psi_args.dest_offset        = args->offset + nbytes;
        psi_args.continuity_counter = args->continuity_counter;
        psi_args.crc                = &crc;

        nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

        /* skip both pointers at the end */
        psi_args.len = sizeof(struct vidtv_psi_table_eit_event) -
                       sizeof(struct vidtv_psi_desc *) -
                       sizeof(struct vidtv_psi_table_eit_event *);
        while (event) {
                /* copy the events, if any */
                psi_args.from = event;
                psi_args.dest_offset = args->offset + nbytes;

                nbytes += vidtv_psi_ts_psi_write_into(&psi_args);

                event_descriptor = event->descriptor;

                while (event_descriptor) {
                        /* copy the event descriptors, if any */
                        d_args.dest_offset        = args->offset + nbytes;
                        d_args.desc               = event_descriptor;
                        d_args.continuity_counter = args->continuity_counter;
                        d_args.crc                = &crc;

                        nbytes += vidtv_psi_desc_write_into(&d_args);

                        event_descriptor = event_descriptor->next;
                }

                event = event->next;
        }

        c_args.dest_offset        = args->offset + nbytes;
        c_args.crc                = cpu_to_be32(crc);
        c_args.continuity_counter = args->continuity_counter;

        /* Write the CRC at the end */
        nbytes += table_section_crc32_write_into(&c_args);

        return nbytes;
}

struct vidtv_psi_table_eit_event
*vidtv_psi_eit_event_init(struct vidtv_psi_table_eit_event *head, u16 event_id)
{
        const u8 DURATION[] = {0x23, 0x59, 0x59}; /* BCD encoded */
        struct vidtv_psi_table_eit_event *e;
        struct timespec64 ts;
        struct tm time;
        int mjd, l;
        __be16 mjd_be;

        e = kzalloc(sizeof(*e), GFP_KERNEL);
        if (!e)
                return NULL;

        e->event_id = cpu_to_be16(event_id);

        ts = ktime_to_timespec64(ktime_get_real());
        time64_to_tm(ts.tv_sec, 0, &time);

        /* Convert date to Modified Julian Date - per EN 300 468 Annex C */
        if (time.tm_mon < 2)
                l = 1;
        else
                l = 0;

        mjd = 14956 + time.tm_mday;
        mjd += (time.tm_year - l) * 36525 / 100;
        mjd += (time.tm_mon + 2 + l * 12) * 306001 / 10000;
        mjd_be = cpu_to_be16(mjd);

        /*
         * Store MJD and hour/min/sec to the event.
         *
         * Let's make the event to start on a full hour
         */
        memcpy(e->start_time, &mjd_be, sizeof(mjd_be));
        e->start_time[2] = bin2bcd(time.tm_hour);
        e->start_time[3] = 0;
        e->start_time[4] = 0;

        /*
         * TODO: for now, the event will last for a day. Should be
         * enough for testing purposes, but if one runs the driver
         * for more than that, the current event will become invalid.
         * So, we need a better code here in order to change the start
         * time once the event expires.
         */
        memcpy(e->duration, DURATION, sizeof(e->duration));

        e->bitfield = cpu_to_be16(RUNNING << 13);

        if (head) {
                while (head->next)
                        head = head->next;

                head->next = e;
        }

        return e;
}

void vidtv_psi_eit_event_destroy(struct vidtv_psi_table_eit_event *e)
{
        struct vidtv_psi_table_eit_event *tmp_e  = NULL;
        struct vidtv_psi_table_eit_event *curr_e = e;

        while (curr_e) {
                tmp_e  = curr_e;
                curr_e = curr_e->next;
                vidtv_psi_desc_destroy(tmp_e->descriptor);
                kfree(tmp_e);
        }
}

void vidtv_psi_eit_table_destroy(struct vidtv_psi_table_eit *eit)
{
        vidtv_psi_eit_event_destroy(eit->event);
        kfree(eit);
}