/*
 * Driver for IBM Power 842 compression accelerator
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Copyright (C) IBM Corporation, 2012
 *
 * Authors: Robert Jennings <rcj@linux.vnet.ibm.com>
 *          Seth Jennings <sjenning@linux.vnet.ibm.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/nx842.h>
#include <linux/of.h>
#include <linux/slab.h>

#include <asm/page.h>
#include <asm/vio.h>

#include "nx_csbcpb.h" /* struct nx_csbcpb */

#define MODULE_NAME "nx-compress"
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Robert Jennings <rcj@linux.vnet.ibm.com>");
MODULE_DESCRIPTION("842 H/W Compression driver for IBM Power processors");

#define SHIFT_4K 12
#define SHIFT_64K 16
#define SIZE_4K (1UL << SHIFT_4K)
#define SIZE_64K (1UL << SHIFT_64K)

/* IO buffer must be 128 byte aligned */
#define IO_BUFFER_ALIGN 128

struct nx842_header {
        int blocks_nr; /* number of compressed blocks */
        int offset; /* offset of the first block (from beginning of header) */
        int sizes[0]; /* size of compressed blocks */
};

static inline int nx842_header_size(const struct nx842_header *hdr)
{
        return sizeof(struct nx842_header) +
                        hdr->blocks_nr * sizeof(hdr->sizes[0]);
}

/* Macros for fields within nx_csbcpb */
/* Check the valid bit within the csbcpb valid field */
#define NX842_CSBCBP_VALID_CHK(x) (x & BIT_MASK(7))

/* CE macros operate on the completion_extension field bits in the csbcpb.
 * CE0 0=full completion, 1=partial completion
 * CE1 0=CE0 indicates completion, 1=termination (output may be modified)
 * CE2 0=processed_bytes is source bytes, 1=processed_bytes is target bytes */
#define NX842_CSBCPB_CE0(x)     (x & BIT_MASK(7))
#define NX842_CSBCPB_CE1(x)     (x & BIT_MASK(6))
#define NX842_CSBCPB_CE2(x)     (x & BIT_MASK(5))

/* The NX unit accepts data only on 4K page boundaries */
#define NX842_HW_PAGE_SHIFT     SHIFT_4K
#define NX842_HW_PAGE_SIZE      (ASM_CONST(1) << NX842_HW_PAGE_SHIFT)
#define NX842_HW_PAGE_MASK      (~(NX842_HW_PAGE_SIZE-1))

enum nx842_status {
        UNAVAILABLE,
        AVAILABLE
};

struct ibm_nx842_counters {
        atomic64_t comp_complete;
        atomic64_t comp_failed;
        atomic64_t decomp_complete;
        atomic64_t decomp_failed;
        atomic64_t swdecomp;
        atomic64_t comp_times[32];
        atomic64_t decomp_times[32];
};

static struct nx842_devdata {
        struct vio_dev *vdev;
        struct device *dev;
        struct ibm_nx842_counters *counters;
        unsigned int max_sg_len;
        unsigned int max_sync_size;
        unsigned int max_sync_sg;
        enum nx842_status status;
} __rcu *devdata;
static DEFINE_SPINLOCK(devdata_mutex);

#define NX842_COUNTER_INC(_x) \
static inline void nx842_inc_##_x( \
        const struct nx842_devdata *dev) { \
        if (dev) \
                atomic64_inc(&dev->counters->_x); \
}
NX842_COUNTER_INC(comp_complete);
NX842_COUNTER_INC(comp_failed);
NX842_COUNTER_INC(decomp_complete);
NX842_COUNTER_INC(decomp_failed);
NX842_COUNTER_INC(swdecomp);

#define NX842_HIST_SLOTS 16

static void ibm_nx842_incr_hist(atomic64_t *times, unsigned int time)
{
        int bucket = fls(time);

        if (bucket)
                bucket = min((NX842_HIST_SLOTS - 1), bucket - 1);

        atomic64_inc(&times[bucket]);
}

/* NX unit operation flags */
#define NX842_OP_COMPRESS       0x0
#define NX842_OP_CRC            0x1
#define NX842_OP_DECOMPRESS     0x2
#define NX842_OP_COMPRESS_CRC   (NX842_OP_COMPRESS | NX842_OP_CRC)
#define NX842_OP_DECOMPRESS_CRC (NX842_OP_DECOMPRESS | NX842_OP_CRC)
#define NX842_OP_ASYNC          (1<<23)
#define NX842_OP_NOTIFY         (1<<22)
#define NX842_OP_NOTIFY_INT(x)  ((x & 0xff)<<8)

static unsigned long nx842_get_desired_dma(struct vio_dev *viodev)
{
        /* No use of DMA mappings within the driver. */
        return 0;
}

struct nx842_slentry {
        unsigned long ptr; /* Real address (use __pa()) */
        unsigned long len;
};

/* pHyp scatterlist entry */
struct nx842_scatterlist {
        int entry_nr; /* number of slentries */
        struct nx842_slentry *entries; /* ptr to array of slentries */
};

/* Does not include sizeof(entry_nr) in the size */
static inline unsigned long nx842_get_scatterlist_size(
                                struct nx842_scatterlist *sl)
{
        return sl->entry_nr * sizeof(struct nx842_slentry);
}

static int nx842_build_scatterlist(unsigned long buf, int len,
                        struct nx842_scatterlist *sl)
{
        unsigned long nextpage;
        struct nx842_slentry *entry;

        sl->entry_nr = 0;

        entry = sl->entries;
        while (len) {
                entry->ptr = __pa(buf);
                nextpage = ALIGN(buf + 1, NX842_HW_PAGE_SIZE);
                if (nextpage < buf + len) {
                        /* we aren't at the end yet */
                        if (IS_ALIGNED(buf, NX842_HW_PAGE_SIZE))
                                /* we are in the middle (or beginning) */
                                entry->len = NX842_HW_PAGE_SIZE;
                        else
                                /* we are at the beginning */
                                entry->len = nextpage - buf;
                } else {
                        /* at the end */
                        entry->len = len;
                }

                len -= entry->len;
                buf += entry->len;
                sl->entry_nr++;
                entry++;
        }

        return 0;
}

/*
 * Working memory for software decompression
 */
struct sw842_fifo {
        union {
                char f8[256][8];
                char f4[512][4];
        };
        char f2[256][2];
        unsigned char f84_full;
        unsigned char f2_full;
        unsigned char f8_count;
        unsigned char f2_count;
        unsigned int f4_count;
};

/*
 * Working memory for crypto API
 */
struct nx842_workmem {
        char bounce[PAGE_SIZE]; /* bounce buffer for decompression input */
        union {
                /* hardware working memory */
                struct {
                        /* scatterlist */
                        char slin[SIZE_4K];
                        char slout[SIZE_4K];
                        /* coprocessor status/parameter block */
                        struct nx_csbcpb csbcpb;
                };
                /* software working memory */
                struct sw842_fifo swfifo; /* software decompression fifo */
        };
};

int nx842_get_workmem_size(void)
{
        return sizeof(struct nx842_workmem) + NX842_HW_PAGE_SIZE;
}
EXPORT_SYMBOL_GPL(nx842_get_workmem_size);

int nx842_get_workmem_size_aligned(void)
{
        return sizeof(struct nx842_workmem);
}
EXPORT_SYMBOL_GPL(nx842_get_workmem_size_aligned);

static int nx842_validate_result(struct device *dev,
        struct cop_status_block *csb)
{
        /* The csb must be valid after returning from vio_h_cop_sync */
        if (!NX842_CSBCBP_VALID_CHK(csb->valid)) {
                dev_err(dev, "%s: cspcbp not valid upon completion.\n",
                                __func__);
                dev_dbg(dev, "valid:0x%02x cs:0x%02x cc:0x%02x ce:0x%02x\n",
                                csb->valid,
                                csb->crb_seq_number,
                                csb->completion_code,
                                csb->completion_extension);
                dev_dbg(dev, "processed_bytes:%d address:0x%016lx\n",
                                csb->processed_byte_count,
                                (unsigned long)csb->address);
                return -EIO;
        }

        /* Check return values from the hardware in the CSB */
        switch (csb->completion_code) {
        case 0: /* Completed without error */
                break;
        case 64: /* Target bytes > Source bytes during compression */
        case 13: /* Output buffer too small */
                dev_dbg(dev, "%s: Compression output larger than input\n",
                                        __func__);
                return -ENOSPC;
        case 66: /* Input data contains an illegal template field */
        case 67: /* Template indicates data past the end of the input stream */
                dev_dbg(dev, "%s: Bad data for decompression (code:%d)\n",
                                        __func__, csb->completion_code);
                return -EINVAL;
        default:
                dev_dbg(dev, "%s: Unspecified error (code:%d)\n",
                                        __func__, csb->completion_code);
                return -EIO;
        }

        /* Hardware sanity check */
        if (!NX842_CSBCPB_CE2(csb->completion_extension)) {
                dev_err(dev, "%s: No error returned by hardware, but "
                                "data returned is unusable, contact support.\n"
                                "(Additional info: csbcbp->processed bytes "
                                "does not specify processed bytes for the "
                                "target buffer.)\n", __func__);
                return -EIO;
        }

        return 0;
}

/**
 * nx842_compress - Compress data using the 842 algorithm
 *
 * Compression provide by the NX842 coprocessor on IBM Power systems.
 * The input buffer is compressed and the result is stored in the
 * provided output buffer.
 *
 * Upon return from this function @outlen contains the length of the
 * compressed data.  If there is an error then @outlen will be 0 and an
 * error will be specified by the return code from this function.
 *
 * @in: Pointer to input buffer, must be page aligned
 * @inlen: Length of input buffer, must be PAGE_SIZE
 * @out: Pointer to output buffer
 * @outlen: Length of output buffer
 * @wrkmem: ptr to buffer for working memory, size determined by
 *          nx842_get_workmem_size()
 *
 * Returns:
 *   0          Success, output of length @outlen stored in the buffer at @out
 *   -ENOMEM    Unable to allocate internal buffers
 *   -ENOSPC    Output buffer is to small
 *   -EMSGSIZE  XXX Difficult to describe this limitation
 *   -EIO       Internal error
 *   -ENODEV    Hardware unavailable
 */
int nx842_compress(const unsigned char *in, unsigned int inlen,
                       unsigned char *out, unsigned int *outlen, void *wmem)
{
        struct nx842_header *hdr;
        struct nx842_devdata *local_devdata;
        struct device *dev = NULL;
        struct nx842_workmem *workmem;
        struct nx842_scatterlist slin, slout;
        struct nx_csbcpb *csbcpb;
        int ret = 0, max_sync_size, i, bytesleft, size, hdrsize;
        unsigned long inbuf, outbuf, padding;
        struct vio_pfo_op op = {
                .done = NULL,
                .handle = 0,
                .timeout = 0,
        };
        unsigned long start_time = get_tb();

        /*
         * Make sure input buffer is 64k page aligned.  This is assumed since
         * this driver is designed for page compression only (for now).  This
         * is very nice since we can now use direct DDE(s) for the input and
         * the alignment is guaranteed.
        */
        inbuf = (unsigned long)in;
        if (!IS_ALIGNED(inbuf, PAGE_SIZE) || inlen != PAGE_SIZE)
                return -EINVAL;

        rcu_read_lock();
        local_devdata = rcu_dereference(devdata);
        if (!local_devdata || !local_devdata->dev) {
                rcu_read_unlock();
                return -ENODEV;
        }
        max_sync_size = local_devdata->max_sync_size;
        dev = local_devdata->dev;

        /* Create the header */
        hdr = (struct nx842_header *)out;
        hdr->blocks_nr = PAGE_SIZE / max_sync_size;
        hdrsize = nx842_header_size(hdr);
        outbuf = (unsigned long)out + hdrsize;
        bytesleft = *outlen - hdrsize;

        /* Init scatterlist */
        workmem = (struct nx842_workmem *)ALIGN((unsigned long)wmem,
                NX842_HW_PAGE_SIZE);
        slin.entries = (struct nx842_slentry *)workmem->slin;
        slout.entries = (struct nx842_slentry *)workmem->slout;

        /* Init operation */
        op.flags = NX842_OP_COMPRESS;
        csbcpb = &workmem->csbcpb;
        memset(csbcpb, 0, sizeof(*csbcpb));
        op.csbcpb = __pa(csbcpb);
        op.out = __pa(slout.entries);

        for (i = 0; i < hdr->blocks_nr; i++) {
                /*
                 * Aligning the output blocks to 128 bytes does waste space,
                 * but it prevents the need for bounce buffers and memory
                 * copies.  It also simplifies the code a lot.  In the worst
                 * case (64k page, 4k max_sync_size), you lose up to
                 * (128*16)/64k = ~3% the compression factor. For 64k
                 * max_sync_size, the loss would be at most 128/64k = ~0.2%.
                 */
                padding = ALIGN(outbuf, IO_BUFFER_ALIGN) - outbuf;
                outbuf += padding;
                bytesleft -= padding;
                if (i == 0)
                        /* save offset into first block in header */
                        hdr->offset = padding + hdrsize;

                if (bytesleft <= 0) {
                        ret = -ENOSPC;
                        goto unlock;
                }

                /*
                 * NOTE: If the default max_sync_size is changed from 4k
                 * to 64k, remove the "likely" case below, since a
                 * scatterlist will always be needed.
                 */
                if (likely(max_sync_size == NX842_HW_PAGE_SIZE)) {
                        /* Create direct DDE */
                        op.in = __pa(inbuf);
                        op.inlen = max_sync_size;

                } else {
                        /* Create indirect DDE (scatterlist) */
                        nx842_build_scatterlist(inbuf, max_sync_size, &slin);
                        op.in = __pa(slin.entries);
                        op.inlen = -nx842_get_scatterlist_size(&slin);
                }

                /*
                 * If max_sync_size != NX842_HW_PAGE_SIZE, an indirect
                 * DDE is required for the outbuf.
                 * If max_sync_size == NX842_HW_PAGE_SIZE, outbuf must
                 * also be page aligned (1 in 128/4k=32 chance) in order
                 * to use a direct DDE.
                 * This is unlikely, just use an indirect DDE always.
                 */
                nx842_build_scatterlist(outbuf,
                        min(bytesleft, max_sync_size), &slout);
                /* op.out set before loop */
                op.outlen = -nx842_get_scatterlist_size(&slout);

                /* Send request to pHyp */
                ret = vio_h_cop_sync(local_devdata->vdev, &op);

                /* Check for pHyp error */
                if (ret) {
                        dev_dbg(dev, "%s: vio_h_cop_sync error (ret=%d, hret=%ld)\n",
                                __func__, ret, op.hcall_err);
                        ret = -EIO;
                        goto unlock;
                }

                /* Check for hardware error */
                ret = nx842_validate_result(dev, &csbcpb->csb);
                if (ret && ret != -ENOSPC)
                        goto unlock;

                /* Handle incompressible data */
                if (unlikely(ret == -ENOSPC)) {
                        if (bytesleft < max_sync_size) {
                                /*
                                 * Not enough space left in the output buffer
                                 * to store uncompressed block
                                 */
                                goto unlock;
                        } else {
                                /* Store incompressible block */
                                memcpy((void *)outbuf, (void *)inbuf,
                                        max_sync_size);
                                hdr->sizes[i] = -max_sync_size;
                                outbuf += max_sync_size;
                                bytesleft -= max_sync_size;
                                /* Reset ret, incompressible data handled */
                                ret = 0;
                        }
                } else {
                        /* Normal case, compression was successful */
                        size = csbcpb->csb.processed_byte_count;
                        dev_dbg(dev, "%s: processed_bytes=%d\n",
                                __func__, size);
                        hdr->sizes[i] = size;
                        outbuf += size;
                        bytesleft -= size;
                }

                inbuf += max_sync_size;
        }

        *outlen = (unsigned int)(outbuf - (unsigned long)out);

unlock:
        if (ret)
                nx842_inc_comp_failed(local_devdata);
        else {
                nx842_inc_comp_complete(local_devdata);
                ibm_nx842_incr_hist(local_devdata->counters->comp_times,
                        (get_tb() - start_time) / tb_ticks_per_usec);
        }
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(nx842_compress);

static int sw842_decompress(const unsigned char *, int, unsigned char *, int *,
                        const void *);

/**
 * nx842_decompress - Decompress data using the 842 algorithm
 *
 * Decompression provide by the NX842 coprocessor on IBM Power systems.
 * The input buffer is decompressed and the result is stored in the
 * provided output buffer.  The size allocated to the output buffer is
 * provided by the caller of this function in @outlen.  Upon return from
 * this function @outlen contains the length of the decompressed data.
 * If there is an error then @outlen will be 0 and an error will be
 * specified by the return code from this function.
 *
 * @in: Pointer to input buffer, will use bounce buffer if not 128 byte
 *      aligned
 * @inlen: Length of input buffer
 * @out: Pointer to output buffer, must be page aligned
 * @outlen: Length of output buffer, must be PAGE_SIZE
 * @wrkmem: ptr to buffer for working memory, size determined by
 *          nx842_get_workmem_size()
 *
 * Returns:
 *   0          Success, output of length @outlen stored in the buffer at @out
 *   -ENODEV    Hardware decompression device is unavailable
 *   -ENOMEM    Unable to allocate internal buffers
 *   -ENOSPC    Output buffer is to small
 *   -EINVAL    Bad input data encountered when attempting decompress
 *   -EIO       Internal error
 */
int nx842_decompress(const unsigned char *in, unsigned int inlen,
                         unsigned char *out, unsigned int *outlen, void *wmem)
{
        struct nx842_header *hdr;
        struct nx842_devdata *local_devdata;
        struct device *dev = NULL;
        struct nx842_workmem *workmem;
        struct nx842_scatterlist slin, slout;
        struct nx_csbcpb *csbcpb;
        int ret = 0, i, size, max_sync_size;
        unsigned long inbuf, outbuf;
        struct vio_pfo_op op = {
                .done = NULL,
                .handle = 0,
                .timeout = 0,
        };
        unsigned long start_time = get_tb();

        /* Ensure page alignment and size */
        outbuf = (unsigned long)out;
        if (!IS_ALIGNED(outbuf, PAGE_SIZE) || *outlen != PAGE_SIZE)
                return -EINVAL;

        rcu_read_lock();
        local_devdata = rcu_dereference(devdata);
        if (local_devdata)
                dev = local_devdata->dev;

        /* Get header */
        hdr = (struct nx842_header *)in;

        workmem = (struct nx842_workmem *)ALIGN((unsigned long)wmem,
                NX842_HW_PAGE_SIZE);

        inbuf = (unsigned long)in + hdr->offset;
        if (likely(!IS_ALIGNED(inbuf, IO_BUFFER_ALIGN))) {
                /* Copy block(s) into bounce buffer for alignment */
                memcpy(workmem->bounce, in + hdr->offset, inlen - hdr->offset);
                inbuf = (unsigned long)workmem->bounce;
        }

        /* Init scatterlist */
        slin.entries = (struct nx842_slentry *)workmem->slin;
        slout.entries = (struct nx842_slentry *)workmem->slout;

        /* Init operation */
        op.flags = NX842_OP_DECOMPRESS;
        csbcpb = &workmem->csbcpb;
        memset(csbcpb, 0, sizeof(*csbcpb));
        op.csbcpb = __pa(csbcpb);

        /*
         * max_sync_size may have changed since compression,
         * so we can't read it from the device info. We need
         * to derive it from hdr->blocks_nr.
         */
        max_sync_size = PAGE_SIZE / hdr->blocks_nr;

        for (i = 0; i < hdr->blocks_nr; i++) {
                /* Skip padding */
                inbuf = ALIGN(inbuf, IO_BUFFER_ALIGN);

                if (hdr->sizes[i] < 0) {
                        /* Negative sizes indicate uncompressed data blocks */
                        size = abs(hdr->sizes[i]);
                        memcpy((void *)outbuf, (void *)inbuf, size);
                        outbuf += size;
                        inbuf += size;
                        continue;
                }

                if (!dev)
                        goto sw;

                /*
                 * The better the compression, the more likely the "likely"
                 * case becomes.
                 */
                if (likely((inbuf & NX842_HW_PAGE_MASK) ==
                        ((inbuf + hdr->sizes[i] - 1) & NX842_HW_PAGE_MASK))) {
                        /* Create direct DDE */
                        op.in = __pa(inbuf);
                        op.inlen = hdr->sizes[i];
                } else {
                        /* Create indirect DDE (scatterlist) */
                        nx842_build_scatterlist(inbuf, hdr->sizes[i] , &slin);
                        op.in = __pa(slin.entries);
                        op.inlen = -nx842_get_scatterlist_size(&slin);
                }

                /*
                 * NOTE: If the default max_sync_size is changed from 4k
                 * to 64k, remove the "likely" case below, since a
                 * scatterlist will always be needed.
                 */
                if (likely(max_sync_size == NX842_HW_PAGE_SIZE)) {
                        /* Create direct DDE */
                        op.out = __pa(outbuf);
                        op.outlen = max_sync_size;
                } else {
                        /* Create indirect DDE (scatterlist) */
                        nx842_build_scatterlist(outbuf, max_sync_size, &slout);
                        op.out = __pa(slout.entries);
                        op.outlen = -nx842_get_scatterlist_size(&slout);
                }

                /* Send request to pHyp */
                ret = vio_h_cop_sync(local_devdata->vdev, &op);

                /* Check for pHyp error */
                if (ret) {
                        dev_dbg(dev, "%s: vio_h_cop_sync error (ret=%d, hret=%ld)\n",
                                __func__, ret, op.hcall_err);
                        dev = NULL;
                        goto sw;
                }

                /* Check for hardware error */
                ret = nx842_validate_result(dev, &csbcpb->csb);
                if (ret) {
                        dev = NULL;
                        goto sw;
                }

                /* HW decompression success */
                inbuf += hdr->sizes[i];
                outbuf += csbcpb->csb.processed_byte_count;
                continue;

sw:
                /* software decompression */
                size = max_sync_size;
                ret = sw842_decompress(
                        (unsigned char *)inbuf, hdr->sizes[i],
                        (unsigned char *)outbuf, &size, wmem);
                if (ret)
                        pr_debug("%s: sw842_decompress failed with %d\n",
                                __func__, ret);

                if (ret) {
                        if (ret != -ENOSPC && ret != -EINVAL &&
                                        ret != -EMSGSIZE)
                                ret = -EIO;
                        goto unlock;
                }

                /* SW decompression success */
                inbuf += hdr->sizes[i];
                outbuf += size;
        }

        *outlen = (unsigned int)(outbuf - (unsigned long)out);

unlock:
        if (ret)
                /* decompress fail */
                nx842_inc_decomp_failed(local_devdata);
        else {
                if (!dev)
                        /* software decompress */
                        nx842_inc_swdecomp(local_devdata);
                nx842_inc_decomp_complete(local_devdata);
                ibm_nx842_incr_hist(local_devdata->counters->decomp_times,
                        (get_tb() - start_time) / tb_ticks_per_usec);
        }

        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(nx842_decompress);

/**
 * nx842_OF_set_defaults -- Set default (disabled) values for devdata
 *
 * @devdata - struct nx842_devdata to update
 *
 * Returns:
 *  0 on success
 *  -ENOENT if @devdata ptr is NULL
 */
static int nx842_OF_set_defaults(struct nx842_devdata *devdata)
{
        if (devdata) {
                devdata->max_sync_size = 0;
                devdata->max_sync_sg = 0;
                devdata->max_sg_len = 0;
                devdata->status = UNAVAILABLE;
                return 0;
        } else
                return -ENOENT;
}

/**
 * nx842_OF_upd_status -- Update the device info from OF status prop
 *
 * The status property indicates if the accelerator is enabled.  If the
 * device is in the OF tree it indicates that the hardware is present.
 * The status field indicates if the device is enabled when the status
 * is 'okay'.  Otherwise the device driver will be disabled.
 *
 * @devdata - struct nx842_devdata to update
 * @prop - struct property point containing the maxsyncop for the update
 *
 * Returns:
 *  0 - Device is available
 *  -EINVAL - Device is not available
 */
static int nx842_OF_upd_status(struct nx842_devdata *devdata,
                                        struct property *prop) {
        int ret = 0;
        const char *status = (const char *)prop->value;

        if (!strncmp(status, "okay", (size_t)prop->length)) {
                devdata->status = AVAILABLE;
        } else {
                dev_info(devdata->dev, "%s: status '%s' is not 'okay'\n",
                                __func__, status);
                devdata->status = UNAVAILABLE;
        }

        return ret;
}

/**
 * nx842_OF_upd_maxsglen -- Update the device info from OF maxsglen prop
 *
 * Definition of the 'ibm,max-sg-len' OF property:
 *  This field indicates the maximum byte length of a scatter list
 *  for the platform facility. It is a single cell encoded as with encode-int.
 *
 * Example:
 *  # od -x ibm,max-sg-len
 *  0000000 0000 0ff0
 *
 *  In this example, the maximum byte length of a scatter list is
 *  0x0ff0 (4,080).
 *
 * @devdata - struct nx842_devdata to update
 * @prop - struct property point containing the maxsyncop for the update
 *
 * Returns:
 *  0 on success
 *  -EINVAL on failure
 */
static int nx842_OF_upd_maxsglen(struct nx842_devdata *devdata,
                                        struct property *prop) {
        int ret = 0;
        const int *maxsglen = prop->value;

        if (prop->length != sizeof(*maxsglen)) {
                dev_err(devdata->dev, "%s: unexpected format for ibm,max-sg-len property\n", __func__);
                dev_dbg(devdata->dev, "%s: ibm,max-sg-len is %d bytes long, expected %lu bytes\n", __func__,
                                prop->length, sizeof(*maxsglen));
                ret = -EINVAL;
        } else {
                devdata->max_sg_len = (unsigned int)min(*maxsglen,
                                (int)NX842_HW_PAGE_SIZE);
        }

        return ret;
}

/**
 * nx842_OF_upd_maxsyncop -- Update the device info from OF maxsyncop prop
 *
 * Definition of the 'ibm,max-sync-cop' OF property:
 *  Two series of cells.  The first series of cells represents the maximums
 *  that can be synchronously compressed. The second series of cells
 *  represents the maximums that can be synchronously decompressed.
 *  1. The first cell in each series contains the count of the number of
 *     data length, scatter list elements pairs that follow – each being
 *     of the form
 *    a. One cell data byte length
 *    b. One cell total number of scatter list elements
 *
 * Example:
 *  # od -x ibm,max-sync-cop
 *  0000000 0000 0001 0000 1000 0000 01fe 0000 0001
 *  0000020 0000 1000 0000 01fe
 *
 *  In this example, compression supports 0x1000 (4,096) data byte length
 *  and 0x1fe (510) total scatter list elements.  Decompression supports
 *  0x1000 (4,096) data byte length and 0x1f3 (510) total scatter list
 *  elements.
 *
 * @devdata - struct nx842_devdata to update
 * @prop - struct property point containing the maxsyncop for the update
 *
 * Returns:
 *  0 on success
 *  -EINVAL on failure
 */
static int nx842_OF_upd_maxsyncop(struct nx842_devdata *devdata,
                                        struct property *prop) {
        int ret = 0;
        const struct maxsynccop_t {
                int comp_elements;
                int comp_data_limit;
                int comp_sg_limit;
                int decomp_elements;
                int decomp_data_limit;
                int decomp_sg_limit;
        } *maxsynccop;

        if (prop->length != sizeof(*maxsynccop)) {
                dev_err(devdata->dev, "%s: unexpected format for ibm,max-sync-cop property\n", __func__);
                dev_dbg(devdata->dev, "%s: ibm,max-sync-cop is %d bytes long, expected %lu bytes\n", __func__, prop->length,
                                sizeof(*maxsynccop));
                ret = -EINVAL;
                goto out;
        }

        maxsynccop = (const struct maxsynccop_t *)prop->value;

        /* Use one limit rather than separate limits for compression and
         * decompression. Set a maximum for this so as not to exceed the
         * size that the header can support and round the value down to
         * the hardware page size (4K) */
        devdata->max_sync_size =
                        (unsigned int)min(maxsynccop->comp_data_limit,
                                        maxsynccop->decomp_data_limit);

        devdata->max_sync_size = min_t(unsigned int, devdata->max_sync_size,
                                        SIZE_64K);

        if (devdata->max_sync_size < SIZE_4K) {
                dev_err(devdata->dev, "%s: hardware max data size (%u) is "
                                "less than the driver minimum, unable to use "
                                "the hardware device\n",
                                __func__, devdata->max_sync_size);
                ret = -EINVAL;
                goto out;
        }

        devdata->max_sync_sg = (unsigned int)min(maxsynccop->comp_sg_limit,
                                                maxsynccop->decomp_sg_limit);
        if (devdata->max_sync_sg < 1) {
                dev_err(devdata->dev, "%s: hardware max sg size (%u) is "
                                "less than the driver minimum, unable to use "
                                "the hardware device\n",
                                __func__, devdata->max_sync_sg);
                ret = -EINVAL;
                goto out;
        }

out:
        return ret;
}

/**
 *
 * nx842_OF_upd -- Handle OF properties updates for the device.
 *
 * Set all properties from the OF tree.  Optionally, a new property
 * can be provided by the @new_prop pointer to overwrite an existing value.
 * The device will remain disabled until all values are valid, this function
 * will return an error for updates unless all values are valid.
 *
 * @new_prop: If not NULL, this property is being updated.  If NULL, update
 *  all properties from the current values in the OF tree.
 *
 * Returns:
 *  0 - Success
 *  -ENOMEM - Could not allocate memory for new devdata structure
 *  -EINVAL - property value not found, new_prop is not a recognized
 *      property for the device or property value is not valid.
 *  -ENODEV - Device is not available
 */
static int nx842_OF_upd(struct property *new_prop)
{
        struct nx842_devdata *old_devdata = NULL;
        struct nx842_devdata *new_devdata = NULL;
        struct device_node *of_node = NULL;
        struct property *status = NULL;
        struct property *maxsglen = NULL;
        struct property *maxsyncop = NULL;
        int ret = 0;
        unsigned long flags;

        spin_lock_irqsave(&devdata_mutex, flags);
        old_devdata = rcu_dereference_check(devdata,
                        lockdep_is_held(&devdata_mutex));
        if (old_devdata)
                of_node = old_devdata->dev->of_node;

        if (!old_devdata || !of_node) {
                pr_err("%s: device is not available\n", __func__);
                spin_unlock_irqrestore(&devdata_mutex, flags);
                return -ENODEV;
        }

        new_devdata = kzalloc(sizeof(*new_devdata), GFP_NOFS);
        if (!new_devdata) {
                dev_err(old_devdata->dev, "%s: Could not allocate memory for device data\n", __func__);
                ret = -ENOMEM;
                goto error_out;
        }

        memcpy(new_devdata, old_devdata, sizeof(*old_devdata));
        new_devdata->counters = old_devdata->counters;

        /* Set ptrs for existing properties */
        status = of_find_property(of_node, "status", NULL);
        maxsglen = of_find_property(of_node, "ibm,max-sg-len", NULL);
        maxsyncop = of_find_property(of_node, "ibm,max-sync-cop", NULL);
        if (!status || !maxsglen || !maxsyncop) {
                dev_err(old_devdata->dev, "%s: Could not locate device properties\n", __func__);
                ret = -EINVAL;
                goto error_out;
        }

        /* Set ptr to new property if provided */
        if (new_prop) {
                /* Single property */
                if (!strncmp(new_prop->name, "status", new_prop->length)) {
                        status = new_prop;

                } else if (!strncmp(new_prop->name, "ibm,max-sg-len",
                                        new_prop->length)) {
                        maxsglen = new_prop;

                } else if (!strncmp(new_prop->name, "ibm,max-sync-cop",
                                        new_prop->length)) {
                        maxsyncop = new_prop;

                } else {
                        /*
                         * Skip the update, the property being updated
                         * has no impact.
                         */
                        goto out;
                }
        }

        /* Perform property updates */
        ret = nx842_OF_upd_status(new_devdata, status);
        if (ret)
                goto error_out;

        ret = nx842_OF_upd_maxsglen(new_devdata, maxsglen);
        if (ret)
                goto error_out;

        ret = nx842_OF_upd_maxsyncop(new_devdata, maxsyncop);
        if (ret)
                goto error_out;

out:
        dev_info(old_devdata->dev, "%s: max_sync_size new:%u old:%u\n",
                        __func__, new_devdata->max_sync_size,
                        old_devdata->max_sync_size);
        dev_info(old_devdata->dev, "%s: max_sync_sg new:%u old:%u\n",
                        __func__, new_devdata->max_sync_sg,
                        old_devdata->max_sync_sg);
        dev_info(old_devdata->dev, "%s: max_sg_len new:%u old:%u\n",
                        __func__, new_devdata->max_sg_len,
                        old_devdata->max_sg_len);

        rcu_assign_pointer(devdata, new_devdata);
        spin_unlock_irqrestore(&devdata_mutex, flags);
        synchronize_rcu();
        dev_set_drvdata(new_devdata->dev, new_devdata);
        kfree(old_devdata);
        return 0;

error_out:
        if (new_devdata) {
                dev_info(old_devdata->dev, "%s: device disabled\n", __func__);
                nx842_OF_set_defaults(new_devdata);
                rcu_assign_pointer(devdata, new_devdata);
                spin_unlock_irqrestore(&devdata_mutex, flags);
                synchronize_rcu();
                dev_set_drvdata(new_devdata->dev, new_devdata);
                kfree(old_devdata);
        } else {
                dev_err(old_devdata->dev, "%s: could not update driver from hardware\n", __func__);
                spin_unlock_irqrestore(&devdata_mutex, flags);
        }

        if (!ret)
                ret = -EINVAL;
        return ret;

}

/**
 * nx842_OF_notifier - Process updates to OF properties for the device
 *
 * @np: notifier block
 * @action: notifier action
 * @update: struct pSeries_reconfig_prop_update pointer if action is
 *      PSERIES_UPDATE_PROPERTY
 *
 * Returns:
 *      NOTIFY_OK on success
 *      NOTIFY_BAD encoded with error number on failure, use
 *              notifier_to_errno() to decode this value
 */
static int nx842_OF_notifier(struct notifier_block *np, unsigned long action,
                             void *update)
{
        struct of_prop_reconfig *upd = update;
        struct nx842_devdata *local_devdata;
        struct device_node *node = NULL;

        rcu_read_lock();
        local_devdata = rcu_dereference(devdata);
        if (local_devdata)
                node = local_devdata->dev->of_node;

        if (local_devdata &&
                        action == OF_RECONFIG_UPDATE_PROPERTY &&
                        !strcmp(upd->dn->name, node->name)) {
                rcu_read_unlock();
                nx842_OF_upd(upd->prop);
        } else
                rcu_read_unlock();

        return NOTIFY_OK;
}

static struct notifier_block nx842_of_nb = {
        .notifier_call = nx842_OF_notifier,
};

#define nx842_counter_read(_name)                                       \
static ssize_t nx842_##_name##_show(struct device *dev,         \
                struct device_attribute *attr,                          \
                char *buf) {                                            \
        struct nx842_devdata *local_devdata;                    \
        int p = 0;                                                      \
        rcu_read_lock();                                                \
        local_devdata = rcu_dereference(devdata);                       \
        if (local_devdata)                                              \
                p = snprintf(buf, PAGE_SIZE, "%ld\n",                   \
                       atomic64_read(&local_devdata->counters->_name)); \
        rcu_read_unlock();                                              \
        return p;                                                       \
}

#define NX842DEV_COUNTER_ATTR_RO(_name)                                 \
        nx842_counter_read(_name);                                      \
        static struct device_attribute dev_attr_##_name = __ATTR(_name, \
                                                0444,                   \
                                                nx842_##_name##_show,\
                                                NULL);

NX842DEV_COUNTER_ATTR_RO(comp_complete);
NX842DEV_COUNTER_ATTR_RO(comp_failed);
NX842DEV_COUNTER_ATTR_RO(decomp_complete);
NX842DEV_COUNTER_ATTR_RO(decomp_failed);
NX842DEV_COUNTER_ATTR_RO(swdecomp);

static ssize_t nx842_timehist_show(struct device *,
                struct device_attribute *, char *);

static struct device_attribute dev_attr_comp_times = __ATTR(comp_times, 0444,
                nx842_timehist_show, NULL);
static struct device_attribute dev_attr_decomp_times = __ATTR(decomp_times,
                0444, nx842_timehist_show, NULL);

static ssize_t nx842_timehist_show(struct device *dev,
                struct device_attribute *attr, char *buf) {
        char *p = buf;
        struct nx842_devdata *local_devdata;
        atomic64_t *times;
        int bytes_remain = PAGE_SIZE;
        int bytes;
        int i;

        rcu_read_lock();
        local_devdata = rcu_dereference(devdata);
        if (!local_devdata) {
                rcu_read_unlock();
                return 0;
        }

        if (attr == &dev_attr_comp_times)
                times = local_devdata->counters->comp_times;
        else if (attr == &dev_attr_decomp_times)
                times = local_devdata->counters->decomp_times;
        else {
                rcu_read_unlock();
                return 0;
        }

        for (i = 0; i < (NX842_HIST_SLOTS - 2); i++) {
                bytes = snprintf(p, bytes_remain, "%u-%uus:\t%ld\n",
                               i ? (2<<(i-1)) : 0, (2<<i)-1,
                               atomic64_read(&times[i]));
                bytes_remain -= bytes;
                p += bytes;
        }
        /* The last bucket holds everything over
         * 2<<(NX842_HIST_SLOTS - 2) us */
        bytes = snprintf(p, bytes_remain, "%uus - :\t%ld\n",
                        2<<(NX842_HIST_SLOTS - 2),
                        atomic64_read(&times[(NX842_HIST_SLOTS - 1)]));
        p += bytes;

        rcu_read_unlock();
        return p - buf;
}

static struct attribute *nx842_sysfs_entries[] = {
        &dev_attr_comp_complete.attr,
        &dev_attr_comp_failed.attr,
        &dev_attr_decomp_complete.attr,
        &dev_attr_decomp_failed.attr,
        &dev_attr_swdecomp.attr,
        &dev_attr_comp_times.attr,
        &dev_attr_decomp_times.attr,
        NULL,
};

static struct attribute_group nx842_attribute_group = {
        .name = NULL,           /* put in device directory */
        .attrs = nx842_sysfs_entries,
};

static int __init nx842_probe(struct vio_dev *viodev,
                                  const struct vio_device_id *id)
{
        struct nx842_devdata *old_devdata, *new_devdata = NULL;
        unsigned long flags;
        int ret = 0;

        spin_lock_irqsave(&devdata_mutex, flags);
        old_devdata = rcu_dereference_check(devdata,
                        lockdep_is_held(&devdata_mutex));

        if (old_devdata && old_devdata->vdev != NULL) {
                dev_err(&viodev->dev, "%s: Attempt to register more than one instance of the hardware\n", __func__);
                ret = -1;
                goto error_unlock;
        }

        dev_set_drvdata(&viodev->dev, NULL);

        new_devdata = kzalloc(sizeof(*new_devdata), GFP_NOFS);
        if (!new_devdata) {
                dev_err(&viodev->dev, "%s: Could not allocate memory for device data\n", __func__);
                ret = -ENOMEM;
                goto error_unlock;
        }

        new_devdata->counters = kzalloc(sizeof(*new_devdata->counters),
                        GFP_NOFS);
        if (!new_devdata->counters) {
                dev_err(&viodev->dev, "%s: Could not allocate memory for performance counters\n", __func__);
                ret = -ENOMEM;
                goto error_unlock;
        }

        new_devdata->vdev = viodev;
        new_devdata->dev = &viodev->dev;
        nx842_OF_set_defaults(new_devdata);

        rcu_assign_pointer(devdata, new_devdata);
        spin_unlock_irqrestore(&devdata_mutex, flags);
        synchronize_rcu();
        kfree(old_devdata);

        of_reconfig_notifier_register(&nx842_of_nb);

        ret = nx842_OF_upd(NULL);
        if (ret && ret != -ENODEV) {
                dev_err(&viodev->dev, "could not parse device tree. %d\n", ret);
                ret = -1;
                goto error;
        }

        rcu_read_lock();
        if (dev_set_drvdata(&viodev->dev, rcu_dereference(devdata))) {
                rcu_read_unlock();
                dev_err(&viodev->dev, "failed to set driver data for device\n");
                ret = -1;
                goto error;
        }
        rcu_read_unlock();

        if (sysfs_create_group(&viodev->dev.kobj, &nx842_attribute_group)) {
                dev_err(&viodev->dev, "could not create sysfs device attributes\n");
                ret = -1;
                goto error;
        }

        return 0;

error_unlock:
        spin_unlock_irqrestore(&devdata_mutex, flags);
        if (new_devdata)
                kfree(new_devdata->counters);
        kfree(new_devdata);
error:
        return ret;
}

static int __exit nx842_remove(struct vio_dev *viodev)
{
        struct nx842_devdata *old_devdata;
        unsigned long flags;

        pr_info("Removing IBM Power 842 compression device\n");
        sysfs_remove_group(&viodev->dev.kobj, &nx842_attribute_group);

        spin_lock_irqsave(&devdata_mutex, flags);
        old_devdata = rcu_dereference_check(devdata,
                        lockdep_is_held(&devdata_mutex));
        of_reconfig_notifier_unregister(&nx842_of_nb);
        rcu_assign_pointer(devdata, NULL);
        spin_unlock_irqrestore(&devdata_mutex, flags);
        synchronize_rcu();
        dev_set_drvdata(&viodev->dev, NULL);
        if (old_devdata)
                kfree(old_devdata->counters);
        kfree(old_devdata);
        return 0;
}

static struct vio_device_id nx842_driver_ids[] = {
        {"ibm,compression-v1", "ibm,compression"},
        {"", ""},
};

static struct vio_driver nx842_driver = {
        .name = MODULE_NAME,
        .probe = nx842_probe,
        .remove = nx842_remove,
        .get_desired_dma = nx842_get_desired_dma,
        .id_table = nx842_driver_ids,
};

static int __init nx842_init(void)
{
        struct nx842_devdata *new_devdata;
        pr_info("Registering IBM Power 842 compression driver\n");

        RCU_INIT_POINTER(devdata, NULL);
        new_devdata = kzalloc(sizeof(*new_devdata), GFP_KERNEL);
        if (!new_devdata) {
                pr_err("Could not allocate memory for device data\n");
                return -ENOMEM;
        }
        new_devdata->status = UNAVAILABLE;
        RCU_INIT_POINTER(devdata, new_devdata);

        return vio_register_driver(&nx842_driver);
}

module_init(nx842_init);

static void __exit nx842_exit(void)
{
        struct nx842_devdata *old_devdata;
        unsigned long flags;

        pr_info("Exiting IBM Power 842 compression driver\n");
        spin_lock_irqsave(&devdata_mutex, flags);
        old_devdata = rcu_dereference_check(devdata,
                        lockdep_is_held(&devdata_mutex));
        rcu_assign_pointer(devdata, NULL);
        spin_unlock_irqrestore(&devdata_mutex, flags);
        synchronize_rcu();
        if (old_devdata)
                dev_set_drvdata(old_devdata->dev, NULL);
        kfree(old_devdata);
        vio_unregister_driver(&nx842_driver);
}

module_exit(nx842_exit);

/*********************************
 * 842 software decompressor
*********************************/
typedef int (*sw842_template_op)(const char **, int *, unsigned char **,
                                                struct sw842_fifo *);

static int sw842_data8(const char **, int *, unsigned char **,
                                                struct sw842_fifo *);
static int sw842_data4(const char **, int *, unsigned char **,
                                                struct sw842_fifo *);
static int sw842_data2(const char **, int *, unsigned char **,
                                                struct sw842_fifo *);
static int sw842_ptr8(const char **, int *, unsigned char **,
                                                struct sw842_fifo *);
static int sw842_ptr4(const char **, int *, unsigned char **,
                                                struct sw842_fifo *);
static int sw842_ptr2(const char **, int *, unsigned char **,
                                                struct sw842_fifo *);

/* special templates */
#define SW842_TMPL_REPEAT 0x1B
#define SW842_TMPL_ZEROS 0x1C
#define SW842_TMPL_EOF 0x1E

static sw842_template_op sw842_tmpl_ops[26][4] = {
        { sw842_data8, NULL}, /* 0 (00000) */
        { sw842_data4, sw842_data2, sw842_ptr2,  NULL},
        { sw842_data4, sw842_ptr2,  sw842_data2, NULL},
        { sw842_data4, sw842_ptr2,  sw842_ptr2,  NULL},
        { sw842_data4, sw842_ptr4,  NULL},
        { sw842_data2, sw842_ptr2,  sw842_data4, NULL},
        { sw842_data2, sw842_ptr2,  sw842_data2, sw842_ptr2},
        { sw842_data2, sw842_ptr2,  sw842_ptr2,  sw842_data2},
        { sw842_data2, sw842_ptr2,  sw842_ptr2,  sw842_ptr2,},
        { sw842_data2, sw842_ptr2,  sw842_ptr4,  NULL},
        { sw842_ptr2,  sw842_data2, sw842_data4, NULL}, /* 10 (01010) */
        { sw842_ptr2,  sw842_data4, sw842_ptr2,  NULL},
        { sw842_ptr2,  sw842_data2, sw842_ptr2,  sw842_data2},
        { sw842_ptr2,  sw842_data2, sw842_ptr2,  sw842_ptr2},
        { sw842_ptr2,  sw842_data2, sw842_ptr4,  NULL},
        { sw842_ptr2,  sw842_ptr2,  sw842_data4, NULL},
        { sw842_ptr2,  sw842_ptr2,  sw842_data2, sw842_ptr2},
        { sw842_ptr2,  sw842_ptr2,  sw842_ptr2,  sw842_data2},
        { sw842_ptr2,  sw842_ptr2,  sw842_ptr2,  sw842_ptr2},
        { sw842_ptr2,  sw842_ptr2,  sw842_ptr4,  NULL},
        { sw842_ptr4,  sw842_data4, NULL}, /* 20 (10100) */
        { sw842_ptr4,  sw842_data2, sw842_ptr2,  NULL},
        { sw842_ptr4,  sw842_ptr2,  sw842_data2, NULL},
        { sw842_ptr4,  sw842_ptr2,  sw842_ptr2,  NULL},
        { sw842_ptr4,  sw842_ptr4,  NULL},
        { sw842_ptr8,  NULL}
};

/* Software decompress helpers */

static uint8_t sw842_get_byte(const char *buf, int bit)
{
        uint8_t tmpl;
        uint16_t tmp;
        tmp = htons(*(uint16_t *)(buf));
        tmp = (uint16_t)(tmp << bit);
        tmp = ntohs(tmp);
        memcpy(&tmpl, &tmp, 1);
        return tmpl;
}

static uint8_t sw842_get_template(const char **buf, int *bit)
{
        uint8_t byte;
        byte = sw842_get_byte(*buf, *bit);
        byte = byte >> 3;
        byte &= 0x1F;
        *buf += (*bit + 5) / 8;
        *bit = (*bit + 5) % 8;
        return byte;
}

/* repeat_count happens to be 5-bit too (like the template) */
static uint8_t sw842_get_repeat_count(const char **buf, int *bit)
{
        uint8_t byte;
        byte = sw842_get_byte(*buf, *bit);
        byte = byte >> 2;
        byte &= 0x3F;
        *buf += (*bit + 6) / 8;
        *bit = (*bit + 6) % 8;
        return byte;
}

static uint8_t sw842_get_ptr2(const char **buf, int *bit)
{
        uint8_t ptr;
        ptr = sw842_get_byte(*buf, *bit);
        (*buf)++;
        return ptr;
}

static uint16_t sw842_get_ptr4(const char **buf, int *bit,
                struct sw842_fifo *fifo)
{
        uint16_t ptr;
        ptr = htons(*(uint16_t *)(*buf));
        ptr = (uint16_t)(ptr << *bit);
        ptr = ptr >> 7;
        ptr &= 0x01FF;
        *buf += (*bit + 9) / 8;
        *bit = (*bit + 9) % 8;
        return ptr;
}

static uint8_t sw842_get_ptr8(const char **buf, int *bit,
                struct sw842_fifo *fifo)
{
        return sw842_get_ptr2(buf, bit);
}

/* Software decompress template ops */

static int sw842_data8(const char **inbuf, int *inbit,
                unsigned char **outbuf, struct sw842_fifo *fifo)
{
        int ret;

        ret = sw842_data4(inbuf, inbit, outbuf, fifo);
        if (ret)
                return ret;
        ret = sw842_data4(inbuf, inbit, outbuf, fifo);
        return ret;
}

static int sw842_data4(const char **inbuf, int *inbit,
                unsigned char **outbuf, struct sw842_fifo *fifo)
{
        int ret;

        ret = sw842_data2(inbuf, inbit, outbuf, fifo);
        if (ret)
                return ret;
        ret = sw842_data2(inbuf, inbit, outbuf, fifo);
        return ret;
}

static int sw842_data2(const char **inbuf, int *inbit,
                unsigned char **outbuf, struct sw842_fifo *fifo)
{
        **outbuf = sw842_get_byte(*inbuf, *inbit);
        (*inbuf)++;
        (*outbuf)++;
        **outbuf = sw842_get_byte(*inbuf, *inbit);
        (*inbuf)++;
        (*outbuf)++;
        return 0;
}

static int sw842_ptr8(const char **inbuf, int *inbit,
                unsigned char **outbuf, struct sw842_fifo *fifo)
{
        uint8_t ptr;
        ptr = sw842_get_ptr8(inbuf, inbit, fifo);
        if (!fifo->f84_full && (ptr >= fifo->f8_count))
                return 1;
        memcpy(*outbuf, fifo->f8[ptr], 8);
        *outbuf += 8;
        return 0;
}

static int sw842_ptr4(const char **inbuf, int *inbit,
                unsigned char **outbuf, struct sw842_fifo *fifo)
{
        uint16_t ptr;
        ptr = sw842_get_ptr4(inbuf, inbit, fifo);
        if (!fifo->f84_full && (ptr >= fifo->f4_count))
                return 1;
        memcpy(*outbuf, fifo->f4[ptr], 4);
        *outbuf += 4;
        return 0;
}

static int sw842_ptr2(const char **inbuf, int *inbit,
                unsigned char **outbuf, struct sw842_fifo *fifo)
{
        uint8_t ptr;
        ptr = sw842_get_ptr2(inbuf, inbit);
        if (!fifo->f2_full && (ptr >= fifo->f2_count))
                return 1;
        memcpy(*outbuf, fifo->f2[ptr], 2);
        *outbuf += 2;
        return 0;
}

static void sw842_copy_to_fifo(const char *buf, struct sw842_fifo *fifo)
{
        unsigned char initial_f2count = fifo->f2_count;

        memcpy(fifo->f8[fifo->f8_count], buf, 8);
        fifo->f4_count += 2;
        fifo->f8_count += 1;

        if (!fifo->f84_full && fifo->f4_count >= 512) {
                fifo->f84_full = 1;
                fifo->f4_count /= 512;
        }

        memcpy(fifo->f2[fifo->f2_count++], buf, 2);
        memcpy(fifo->f2[fifo->f2_count++], buf + 2, 2);
        memcpy(fifo->f2[fifo->f2_count++], buf + 4, 2);
        memcpy(fifo->f2[fifo->f2_count++], buf + 6, 2);
        if (fifo->f2_count < initial_f2count)
                fifo->f2_full = 1;
}

static int sw842_decompress(const unsigned char *src, int srclen,
                        unsigned char *dst, int *destlen,
                        const void *wrkmem)
{
        uint8_t tmpl;
        const char *inbuf;
        int inbit = 0;
        unsigned char *outbuf, *outbuf_end, *origbuf, *prevbuf;
        const char *inbuf_end;
        sw842_template_op op;
        int opindex;
        int i, repeat_count;
        struct sw842_fifo *fifo;
        int ret = 0;

        fifo = &((struct nx842_workmem *)(wrkmem))->swfifo;
        memset(fifo, 0, sizeof(*fifo));

        origbuf = NULL;
        inbuf = src;
        inbuf_end = src + srclen;
        outbuf = dst;
        outbuf_end = dst + *destlen;

        while ((tmpl = sw842_get_template(&inbuf, &inbit)) != SW842_TMPL_EOF) {
                if (inbuf >= inbuf_end) {
                        ret = -EINVAL;
                        goto out;
                }

                opindex = 0;
                prevbuf = origbuf;
                origbuf = outbuf;
                switch (tmpl) {
                case SW842_TMPL_REPEAT:
                        if (prevbuf == NULL) {
                                ret = -EINVAL;
                                goto out;
                        }

                        repeat_count = sw842_get_repeat_count(&inbuf,
                                                                &inbit) + 1;

                        /* Did the repeat count advance past the end of input */
                        if (inbuf > inbuf_end) {
                                ret = -EINVAL;
                                goto out;
                        }

                        for (i = 0; i < repeat_count; i++) {
                                /* Would this overflow the output buffer */
                                if ((outbuf + 8) > outbuf_end) {
                                        ret = -ENOSPC;
                                        goto out;
                                }

                                memcpy(outbuf, prevbuf, 8);
                                sw842_copy_to_fifo(outbuf, fifo);
                                outbuf += 8;
                        }
                        break;

                case SW842_TMPL_ZEROS:
                        /* Would this overflow the output buffer */
                        if ((outbuf + 8) > outbuf_end) {
                                ret = -ENOSPC;
                                goto out;
                        }

                        memset(outbuf, 0, 8);
                        sw842_copy_to_fifo(outbuf, fifo);
                        outbuf += 8;
                        break;

                default:
                        if (tmpl > 25) {
                                ret = -EINVAL;
                                goto out;
                        }

                        /* Does this go past the end of the input buffer */
                        if ((inbuf + 2) > inbuf_end) {
                                ret = -EINVAL;
                                goto out;
                        }

                        /* Would this overflow the output buffer */
                        if ((outbuf + 8) > outbuf_end) {
                                ret = -ENOSPC;
                                goto out;
                        }

                        while (opindex < 4 &&
                                (op = sw842_tmpl_ops[tmpl][opindex++])
                                        != NULL) {
                                ret = (*op)(&inbuf, &inbit, &outbuf, fifo);
                                if (ret) {
                                        ret = -EINVAL;
                                        goto out;
                                }
                                sw842_copy_to_fifo(origbuf, fifo);
                        }
                }
        }

out:
        if (!ret)
                *destlen = (unsigned int)(outbuf - dst);
        else
                *destlen = 0;

        return ret;
}