// SPDX-License-Identifier: GPL-2.0-only
/*
 * helper functions for vmalloc video4linux capture buffers
 *
 * The functions expect the hardware being able to scatter gather
 * (i.e. the buffers are not linear in physical memory, but fragmented
 * into PAGE_SIZE chunks).  They also assume the driver does not need
 * to touch the video data.
 *
 * (c) 2007 Mauro Carvalho Chehab <mchehab@kernel.org>
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/pgtable.h>

#include <linux/pci.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <asm/page.h>

#include <media/videobuf-vmalloc.h>

#define MAGIC_DMABUF   0x17760309
#define MAGIC_VMAL_MEM 0x18221223

#define MAGIC_CHECK(is, should)                                         \
        if (unlikely((is) != (should))) {                               \
                printk(KERN_ERR "magic mismatch: %x (expected %x)\n",   \
                                is, should);                            \
                BUG();                                                  \
        }

static int debug;
module_param(debug, int, 0644);

MODULE_DESCRIPTION("helper module to manage video4linux vmalloc buffers");
MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@kernel.org>");
MODULE_LICENSE("GPL");

#define dprintk(level, fmt, arg...)                                     \
        if (debug >= level)                                             \
                printk(KERN_DEBUG "vbuf-vmalloc: " fmt , ## arg)


/***************************************************************************/

static void videobuf_vm_open(struct vm_area_struct *vma)
{
        struct videobuf_mapping *map = vma->vm_private_data;

        dprintk(2, "vm_open %p [count=%u,vma=%08lx-%08lx]\n", map,
                map->count, vma->vm_start, vma->vm_end);

        map->count++;
}

static void videobuf_vm_close(struct vm_area_struct *vma)
{
        struct videobuf_mapping *map = vma->vm_private_data;
        struct videobuf_queue *q = map->q;
        int i;

        dprintk(2, "vm_close %p [count=%u,vma=%08lx-%08lx]\n", map,
                map->count, vma->vm_start, vma->vm_end);

        map->count--;
        if (0 == map->count) {
                struct videobuf_vmalloc_memory *mem;

                dprintk(1, "munmap %p q=%p\n", map, q);
                videobuf_queue_lock(q);

                /* We need first to cancel streams, before unmapping */
                if (q->streaming)
                        videobuf_queue_cancel(q);

                for (i = 0; i < VIDEO_MAX_FRAME; i++) {
                        if (NULL == q->bufs[i])
                                continue;

                        if (q->bufs[i]->map != map)
                                continue;

                        mem = q->bufs[i]->priv;
                        if (mem) {
                                /* This callback is called only if kernel has
                                   allocated memory and this memory is mmapped.
                                   In this case, memory should be freed,
                                   in order to do memory unmap.
                                 */

                                MAGIC_CHECK(mem->magic, MAGIC_VMAL_MEM);

                                /* vfree is not atomic - can't be
                                   called with IRQ's disabled
                                 */
                                dprintk(1, "%s: buf[%d] freeing (%p)\n",
                                        __func__, i, mem->vaddr);

                                vfree(mem->vaddr);
                                mem->vaddr = NULL;
                        }

                        q->bufs[i]->map   = NULL;
                        q->bufs[i]->baddr = 0;
                }

                kfree(map);

                videobuf_queue_unlock(q);
        }

        return;
}

static const struct vm_operations_struct videobuf_vm_ops = {
        .open     = videobuf_vm_open,
        .close    = videobuf_vm_close,
};

/* ---------------------------------------------------------------------
 * vmalloc handlers for the generic methods
 */

/* Allocated area consists on 3 parts:
        struct video_buffer
        struct <driver>_buffer (cx88_buffer, saa7134_buf, ...)
        struct videobuf_dma_sg_memory
 */

static struct videobuf_buffer *__videobuf_alloc_vb(size_t size)
{
        struct videobuf_vmalloc_memory *mem;
        struct videobuf_buffer *vb;

        vb = kzalloc(size + sizeof(*mem), GFP_KERNEL);
        if (!vb)
                return vb;

        mem = vb->priv = ((char *)vb) + size;
        mem->magic = MAGIC_VMAL_MEM;

        dprintk(1, "%s: allocated at %p(%ld+%ld) & %p(%ld)\n",
                __func__, vb, (long)sizeof(*vb), (long)size - sizeof(*vb),
                mem, (long)sizeof(*mem));

        return vb;
}

static int __videobuf_iolock(struct videobuf_queue *q,
                             struct videobuf_buffer *vb,
                             struct v4l2_framebuffer *fbuf)
{
        struct videobuf_vmalloc_memory *mem = vb->priv;
        int pages;

        BUG_ON(!mem);

        MAGIC_CHECK(mem->magic, MAGIC_VMAL_MEM);

        switch (vb->memory) {
        case V4L2_MEMORY_MMAP:
                dprintk(1, "%s memory method MMAP\n", __func__);

                /* All handling should be done by __videobuf_mmap_mapper() */
                if (!mem->vaddr) {
                        printk(KERN_ERR "memory is not allocated/mmapped.\n");
                        return -EINVAL;
                }
                break;
        case V4L2_MEMORY_USERPTR:
                pages = PAGE_ALIGN(vb->size);

                dprintk(1, "%s memory method USERPTR\n", __func__);

                if (vb->baddr) {
                        printk(KERN_ERR "USERPTR is currently not supported\n");
                        return -EINVAL;
                }

                /* The only USERPTR currently supported is the one needed for
                 * read() method.
                 */

                mem->vaddr = vmalloc_user(pages);
                if (!mem->vaddr) {
                        printk(KERN_ERR "vmalloc (%d pages) failed\n", pages);
                        return -ENOMEM;
                }
                dprintk(1, "vmalloc is at addr %p (%d pages)\n",
                        mem->vaddr, pages);
                break;
        case V4L2_MEMORY_OVERLAY:
        default:
                dprintk(1, "%s memory method OVERLAY/unknown\n", __func__);

                /* Currently, doesn't support V4L2_MEMORY_OVERLAY */
                printk(KERN_ERR "Memory method currently unsupported.\n");
                return -EINVAL;
        }

        return 0;
}

static int __videobuf_mmap_mapper(struct videobuf_queue *q,
                                  struct videobuf_buffer *buf,
                                  struct vm_area_struct *vma)
{
        struct videobuf_vmalloc_memory *mem;
        struct videobuf_mapping *map;
        int retval, pages;

        dprintk(1, "%s\n", __func__);

        /* create mapping + update buffer list */
        map = kzalloc(sizeof(struct videobuf_mapping), GFP_KERNEL);
        if (NULL == map)
                return -ENOMEM;

        buf->map = map;
        map->q     = q;

        buf->baddr = vma->vm_start;

        mem = buf->priv;
        BUG_ON(!mem);
        MAGIC_CHECK(mem->magic, MAGIC_VMAL_MEM);

        pages = PAGE_ALIGN(vma->vm_end - vma->vm_start);
        mem->vaddr = vmalloc_user(pages);
        if (!mem->vaddr) {
                printk(KERN_ERR "vmalloc (%d pages) failed\n", pages);
                goto error;
        }
        dprintk(1, "vmalloc is at addr %p (%d pages)\n", mem->vaddr, pages);

        /* Try to remap memory */
        retval = remap_vmalloc_range(vma, mem->vaddr, 0);
        if (retval < 0) {
                printk(KERN_ERR "mmap: remap failed with error %d. ", retval);
                vfree(mem->vaddr);
                goto error;
        }

        vma->vm_ops          = &videobuf_vm_ops;
        vma->vm_flags       |= VM_DONTEXPAND | VM_DONTDUMP;
        vma->vm_private_data = map;

        dprintk(1, "mmap %p: q=%p %08lx-%08lx (%lx) pgoff %08lx buf %d\n",
                map, q, vma->vm_start, vma->vm_end,
                (long int)buf->bsize,
                vma->vm_pgoff, buf->i);

        videobuf_vm_open(vma);

        return 0;

error:
        mem = NULL;
        kfree(map);
        return -ENOMEM;
}

static struct videobuf_qtype_ops qops = {
        .magic        = MAGIC_QTYPE_OPS,

        .alloc_vb     = __videobuf_alloc_vb,
        .iolock       = __videobuf_iolock,
        .mmap_mapper  = __videobuf_mmap_mapper,
        .vaddr        = videobuf_to_vmalloc,
};

void videobuf_queue_vmalloc_init(struct videobuf_queue *q,
                         const struct videobuf_queue_ops *ops,
                         struct device *dev,
                         spinlock_t *irqlock,
                         enum v4l2_buf_type type,
                         enum v4l2_field field,
                         unsigned int msize,
                         void *priv,
                         struct mutex *ext_lock)
{
        videobuf_queue_core_init(q, ops, dev, irqlock, type, field, msize,
                                 priv, &qops, ext_lock);
}
EXPORT_SYMBOL_GPL(videobuf_queue_vmalloc_init);

void *videobuf_to_vmalloc(struct videobuf_buffer *buf)
{
        struct videobuf_vmalloc_memory *mem = buf->priv;
        BUG_ON(!mem);
        MAGIC_CHECK(mem->magic, MAGIC_VMAL_MEM);

        return mem->vaddr;
}
EXPORT_SYMBOL_GPL(videobuf_to_vmalloc);

void videobuf_vmalloc_free(struct videobuf_buffer *buf)
{
        struct videobuf_vmalloc_memory *mem = buf->priv;

        /* mmapped memory can't be freed here, otherwise mmapped region
           would be released, while still needed. In this case, the memory
           release should happen inside videobuf_vm_close().
           So, it should free memory only if the memory were allocated for
           read() operation.
         */
        if ((buf->memory != V4L2_MEMORY_USERPTR) || buf->baddr)
                return;

        if (!mem)
                return;

        MAGIC_CHECK(mem->magic, MAGIC_VMAL_MEM);

        vfree(mem->vaddr);
        mem->vaddr = NULL;

        return;
}
EXPORT_SYMBOL_GPL(videobuf_vmalloc_free);