text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * helper functions for SG DMA 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>
   *
   * Highly based on video-buf written originally by:
   * (c) 2001,02 Gerd Knorr <kraxel@bytesex.org>
   * (c) 2006 Mauro Carvalho Chehab, <mchehab@kernel.org>
   * (c) 2006 Ted Walther and John Sokol
   */
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/sched/mm.h>
  #include <linux/slab.h>
  #include <linux/interrupt.h>
  
  #include <linux/dma-mapping.h>
  #include <linux/vmalloc.h>
  #include <linux/pagemap.h>
  #include <linux/scatterlist.h>
  #include <asm/page.h>
  #include <asm/pgtable.h>
  
  #include <media/videobuf-dma-sg.h>
  
  #define MAGIC_DMABUF 0x19721112
  #define MAGIC_SG_MEM 0x17890714
  
  #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 dma sg buffers");
  MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@kernel.org>");
  MODULE_LICENSE("GPL");
  
  #define dprintk(level, fmt, arg...)					\
  	if (debug >= level)						\
  		printk(KERN_DEBUG "vbuf-sg: " fmt , ## arg)
  
  /* --------------------------------------------------------------------- */
  
  /*
   * Return a scatterlist for some page-aligned vmalloc()'ed memory
   * block (NULL on errors).  Memory for the scatterlist is allocated
   * using kmalloc.  The caller must free the memory.
   */
  static struct scatterlist *videobuf_vmalloc_to_sg(unsigned char *virt,
  						  int nr_pages)
  {
  	struct scatterlist *sglist;
  	struct page *pg;
  	int i;
  
  	sglist = vzalloc(array_size(nr_pages, sizeof(*sglist)));
  	if (NULL == sglist)
  		return NULL;
  	sg_init_table(sglist, nr_pages);
  	for (i = 0; i < nr_pages; i++, virt += PAGE_SIZE) {
  		pg = vmalloc_to_page(virt);
  		if (NULL == pg)
  			goto err;
  		BUG_ON(PageHighMem(pg));
  		sg_set_page(&sglist[i], pg, PAGE_SIZE, 0);
  	}
  	return sglist;
  
  err:
  	vfree(sglist);
  	return NULL;
  }
  
  /*
   * Return a scatterlist for a an array of userpages (NULL on errors).
   * Memory for the scatterlist is allocated using kmalloc.  The caller
   * must free the memory.
   */
  static struct scatterlist *videobuf_pages_to_sg(struct page **pages,
  					int nr_pages, int offset, size_t size)
  {
  	struct scatterlist *sglist;
  	int i;
  
  	if (NULL == pages[0])
  		return NULL;
  	sglist = vmalloc(array_size(nr_pages, sizeof(*sglist)));
  	if (NULL == sglist)
  		return NULL;
  	sg_init_table(sglist, nr_pages);
  
  	if (PageHighMem(pages[0]))
  		/* DMA to highmem pages might not work */
  		goto highmem;
  	sg_set_page(&sglist[0], pages[0],
  			min_t(size_t, PAGE_SIZE - offset, size), offset);
  	size -= min_t(size_t, PAGE_SIZE - offset, size);
  	for (i = 1; i < nr_pages; i++) {
  		if (NULL == pages[i])
  			goto nopage;
  		if (PageHighMem(pages[i]))
  			goto highmem;
  		sg_set_page(&sglist[i], pages[i], min_t(size_t, PAGE_SIZE, size), 0);
  		size -= min_t(size_t, PAGE_SIZE, size);
  	}
  	return sglist;
  
  nopage:
  	dprintk(2, "sgl: oops - no page\n");
  	vfree(sglist);
  	return NULL;
  
  highmem:
  	dprintk(2, "sgl: oops - highmem page\n");
  	vfree(sglist);
  	return NULL;
  }
  
  /* --------------------------------------------------------------------- */
  
  struct videobuf_dmabuf *videobuf_to_dma(struct videobuf_buffer *buf)
  {
  	struct videobuf_dma_sg_memory *mem = buf->priv;
  	BUG_ON(!mem);
  
  	MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
  
  	return &mem->dma;
  }
  EXPORT_SYMBOL_GPL(videobuf_to_dma);
  
  static void videobuf_dma_init(struct videobuf_dmabuf *dma)
  {
  	memset(dma, 0, sizeof(*dma));
  	dma->magic = MAGIC_DMABUF;
  }
  
  static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma,
  			int direction, unsigned long data, unsigned long size)
  {
  	unsigned long first, last;
  	int err, rw = 0;
  	unsigned int flags = FOLL_FORCE;
  
  	dma->direction = direction;
  	switch (dma->direction) {
  	case DMA_FROM_DEVICE:
  		rw = READ;
  		break;
  	case DMA_TO_DEVICE:
  		rw = WRITE;
  		break;
  	default:
  		BUG();
  	}
  
  	first = (data          & PAGE_MASK) >> PAGE_SHIFT;
  	last  = ((data+size-1) & PAGE_MASK) >> PAGE_SHIFT;
  	dma->offset = data & ~PAGE_MASK;
  	dma->size = size;
  	dma->nr_pages = last-first+1;
  	dma->pages = kmalloc_array(dma->nr_pages, sizeof(struct page *),
  				   GFP_KERNEL);
  	if (NULL == dma->pages)
  		return -ENOMEM;
  
  	if (rw == READ)
  		flags |= FOLL_WRITE;
  
  	dprintk(1, "init user [0x%lx+0x%lx => %d pages]\n",
  		data, size, dma->nr_pages);
  
  	err = get_user_pages(data & PAGE_MASK, dma->nr_pages,
  			     flags | FOLL_LONGTERM, dma->pages, NULL);
  
  	if (err != dma->nr_pages) {
  		dma->nr_pages = (err >= 0) ? err : 0;
  		dprintk(1, "get_user_pages: err=%d [%d]\n", err,
  			dma->nr_pages);
  		return err < 0 ? err : -EINVAL;
  	}
  	return 0;
  }
  
  static int videobuf_dma_init_user(struct videobuf_dmabuf *dma, int direction,
  			   unsigned long data, unsigned long size)
  {
  	int ret;
  
  	down_read(&current->mm->mmap_sem);
  	ret = videobuf_dma_init_user_locked(dma, direction, data, size);
  	up_read(&current->mm->mmap_sem);
  
  	return ret;
  }
  
  static int videobuf_dma_init_kernel(struct videobuf_dmabuf *dma, int direction,
  			     int nr_pages)
  {
  	int i;
  
  	dprintk(1, "init kernel [%d pages]\n", nr_pages);
  
  	dma->direction = direction;
  	dma->vaddr_pages = kcalloc(nr_pages, sizeof(*dma->vaddr_pages),
  				   GFP_KERNEL);
  	if (!dma->vaddr_pages)
  		return -ENOMEM;
  
  	dma->dma_addr = kcalloc(nr_pages, sizeof(*dma->dma_addr), GFP_KERNEL);
  	if (!dma->dma_addr) {
  		kfree(dma->vaddr_pages);
  		return -ENOMEM;
  	}
  	for (i = 0; i < nr_pages; i++) {
  		void *addr;
  
  		addr = dma_alloc_coherent(dma->dev, PAGE_SIZE,
  					  &(dma->dma_addr[i]), GFP_KERNEL);
  		if (addr == NULL)
  			goto out_free_pages;
  
  		dma->vaddr_pages[i] = virt_to_page(addr);
  	}
  	dma->vaddr = vmap(dma->vaddr_pages, nr_pages, VM_MAP | VM_IOREMAP,
  			  PAGE_KERNEL);
  	if (NULL == dma->vaddr) {
  		dprintk(1, "vmalloc_32(%d pages) failed\n", nr_pages);
  		goto out_free_pages;
  	}
  
  	dprintk(1, "vmalloc is at addr %p, size=%d\n",
  		dma->vaddr, nr_pages << PAGE_SHIFT);
  
  	memset(dma->vaddr, 0, nr_pages << PAGE_SHIFT);
  	dma->nr_pages = nr_pages;
  
  	return 0;
  out_free_pages:
  	while (i > 0) {
  		void *addr;
  
  		i--;
  		addr = page_address(dma->vaddr_pages[i]);
  		dma_free_coherent(dma->dev, PAGE_SIZE, addr, dma->dma_addr[i]);
  	}
  	kfree(dma->dma_addr);
  	dma->dma_addr = NULL;
  	kfree(dma->vaddr_pages);
  	dma->vaddr_pages = NULL;
  
  	return -ENOMEM;
  
  }
  
  static int videobuf_dma_init_overlay(struct videobuf_dmabuf *dma, int direction,
  			      dma_addr_t addr, int nr_pages)
  {
  	dprintk(1, "init overlay [%d pages @ bus 0x%lx]\n",
  		nr_pages, (unsigned long)addr);
  	dma->direction = direction;
  
  	if (0 == addr)
  		return -EINVAL;
  
  	dma->bus_addr = addr;
  	dma->nr_pages = nr_pages;
  
  	return 0;
  }
  
  static int videobuf_dma_map(struct device *dev, struct videobuf_dmabuf *dma)
  {
  	MAGIC_CHECK(dma->magic, MAGIC_DMABUF);
  	BUG_ON(0 == dma->nr_pages);
  
  	if (dma->pages) {
  		dma->sglist = videobuf_pages_to_sg(dma->pages, dma->nr_pages,
  						   dma->offset, dma->size);
  	}
  	if (dma->vaddr) {
  		dma->sglist = videobuf_vmalloc_to_sg(dma->vaddr,
  						     dma->nr_pages);
  	}
  	if (dma->bus_addr) {
  		dma->sglist = vmalloc(sizeof(*dma->sglist));
  		if (NULL != dma->sglist) {
  			dma->sglen = 1;
  			sg_dma_address(&dma->sglist[0])	= dma->bus_addr
  							& PAGE_MASK;
  			dma->sglist[0].offset = dma->bus_addr & ~PAGE_MASK;
  			sg_dma_len(&dma->sglist[0]) = dma->nr_pages * PAGE_SIZE;
  		}
  	}
  	if (NULL == dma->sglist) {
  		dprintk(1, "scatterlist is NULL\n");
  		return -ENOMEM;
  	}
  	if (!dma->bus_addr) {
  		dma->sglen = dma_map_sg(dev, dma->sglist,
  					dma->nr_pages, dma->direction);
  		if (0 == dma->sglen) {
  			printk(KERN_WARNING
  			       "%s: videobuf_map_sg failed\n", __func__);
  			vfree(dma->sglist);
  			dma->sglist = NULL;
  			dma->sglen = 0;
  			return -ENOMEM;
  		}
  	}
  
  	return 0;
  }
  
  int videobuf_dma_unmap(struct device *dev, struct videobuf_dmabuf *dma)
  {
  	MAGIC_CHECK(dma->magic, MAGIC_DMABUF);
  
  	if (!dma->sglen)
  		return 0;
  
  	dma_unmap_sg(dev, dma->sglist, dma->nr_pages, dma->direction);
  
  	vfree(dma->sglist);
  	dma->sglist = NULL;
  	dma->sglen = 0;
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(videobuf_dma_unmap);
  
  int videobuf_dma_free(struct videobuf_dmabuf *dma)
  {
  	int i;
  	MAGIC_CHECK(dma->magic, MAGIC_DMABUF);
  	BUG_ON(dma->sglen);
  
  	if (dma->pages) {
  		for (i = 0; i < dma->nr_pages; i++)
  			put_page(dma->pages[i]);
  		kfree(dma->pages);
  		dma->pages = NULL;
  	}
  
  	if (dma->dma_addr) {
  		for (i = 0; i < dma->nr_pages; i++) {
  			void *addr;
  
  			addr = page_address(dma->vaddr_pages[i]);
  			dma_free_coherent(dma->dev, PAGE_SIZE, addr,
  					  dma->dma_addr[i]);
  		}
  		kfree(dma->dma_addr);
  		dma->dma_addr = NULL;
  		kfree(dma->vaddr_pages);
  		dma->vaddr_pages = NULL;
  		vunmap(dma->vaddr);
  		dma->vaddr = NULL;
  	}
  
  	if (dma->bus_addr)
  		dma->bus_addr = 0;
  	dma->direction = DMA_NONE;
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(videobuf_dma_free);
  
  /* --------------------------------------------------------------------- */
  
  static void videobuf_vm_open(struct vm_area_struct *vma)
  {
  	struct videobuf_mapping *map = vma->vm_private_data;
  
  	dprintk(2, "vm_open %p [count=%d,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;
  	struct videobuf_dma_sg_memory *mem;
  	int i;
  
  	dprintk(2, "vm_close %p [count=%d,vma=%08lx-%08lx]\n", map,
  		map->count, vma->vm_start, vma->vm_end);
  
  	map->count--;
  	if (0 == map->count) {
  		dprintk(1, "munmap %p q=%p\n", map, q);
  		videobuf_queue_lock(q);
  		for (i = 0; i < VIDEO_MAX_FRAME; i++) {
  			if (NULL == q->bufs[i])
  				continue;
  			mem = q->bufs[i]->priv;
  			if (!mem)
  				continue;
  
  			MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
  
  			if (q->bufs[i]->map != map)
  				continue;
  			q->bufs[i]->map   = NULL;
  			q->bufs[i]->baddr = 0;
  			q->ops->buf_release(q, q->bufs[i]);
  		}
  		videobuf_queue_unlock(q);
  		kfree(map);
  	}
  	return;
  }
  
  /*
   * Get a anonymous page for the mapping.  Make sure we can DMA to that
   * memory location with 32bit PCI devices (i.e. don't use highmem for
   * now ...).  Bounce buffers don't work very well for the data rates
   * video capture has.
   */
  static vm_fault_t videobuf_vm_fault(struct vm_fault *vmf)
  {
  	struct vm_area_struct *vma = vmf->vma;
  	struct page *page;
  
  	dprintk(3, "fault: fault @ %08lx [vma %08lx-%08lx]\n",
  		vmf->address, vma->vm_start, vma->vm_end);
  
  	page = alloc_page(GFP_USER | __GFP_DMA32);
  	if (!page)
  		return VM_FAULT_OOM;
  	clear_user_highpage(page, vmf->address);
  	vmf->page = page;
  
  	return 0;
  }
  
  static const struct vm_operations_struct videobuf_vm_ops = {
  	.open	= videobuf_vm_open,
  	.close	= videobuf_vm_close,
  	.fault	= videobuf_vm_fault,
  };
  
  /* ---------------------------------------------------------------------
   * SG 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_dma_sg_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_SG_MEM;
  
  	videobuf_dma_init(&mem->dma);
  
  	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 void *__videobuf_to_vaddr(struct videobuf_buffer *buf)
  {
  	struct videobuf_dma_sg_memory *mem = buf->priv;
  	BUG_ON(!mem);
  
  	MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
  
  	return mem->dma.vaddr;
  }
  
  static int __videobuf_iolock(struct videobuf_queue *q,
  			     struct videobuf_buffer *vb,
  			     struct v4l2_framebuffer *fbuf)
  {
  	int err, pages;
  	dma_addr_t bus;
  	struct videobuf_dma_sg_memory *mem = vb->priv;
  	BUG_ON(!mem);
  
  	MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
  
  	if (!mem->dma.dev)
  		mem->dma.dev = q->dev;
  	else
  		WARN_ON(mem->dma.dev != q->dev);
  
  	switch (vb->memory) {
  	case V4L2_MEMORY_MMAP:
  	case V4L2_MEMORY_USERPTR:
  		if (0 == vb->baddr) {
  			/* no userspace addr -- kernel bounce buffer */
  			pages = PAGE_ALIGN(vb->size) >> PAGE_SHIFT;
  			err = videobuf_dma_init_kernel(&mem->dma,
  						       DMA_FROM_DEVICE,
  						       pages);
  			if (0 != err)
  				return err;
  		} else if (vb->memory == V4L2_MEMORY_USERPTR) {
  			/* dma directly to userspace */
  			err = videobuf_dma_init_user(&mem->dma,
  						     DMA_FROM_DEVICE,
  						     vb->baddr, vb->bsize);
  			if (0 != err)
  				return err;
  		} else {
  			/* NOTE: HACK: videobuf_iolock on V4L2_MEMORY_MMAP
  			buffers can only be called from videobuf_qbuf
  			we take current->mm->mmap_sem there, to prevent
  			locking inversion, so don't take it here */
  
  			err = videobuf_dma_init_user_locked(&mem->dma,
  						      DMA_FROM_DEVICE,
  						      vb->baddr, vb->bsize);
  			if (0 != err)
  				return err;
  		}
  		break;
  	case V4L2_MEMORY_OVERLAY:
  		if (NULL == fbuf)
  			return -EINVAL;
  		/* FIXME: need sanity checks for vb->boff */
  		/*
  		 * Using a double cast to avoid compiler warnings when
  		 * building for PAE. Compiler doesn't like direct casting
  		 * of a 32 bit ptr to 64 bit integer.
  		 */
  		bus   = (dma_addr_t)(unsigned long)fbuf->base + vb->boff;
  		pages = PAGE_ALIGN(vb->size) >> PAGE_SHIFT;
  		err = videobuf_dma_init_overlay(&mem->dma, DMA_FROM_DEVICE,
  						bus, pages);
  		if (0 != err)
  			return err;
  		break;
  	default:
  		BUG();
  	}
  	err = videobuf_dma_map(q->dev, &mem->dma);
  	if (0 != err)
  		return err;
  
  	return 0;
  }
  
  static int __videobuf_sync(struct videobuf_queue *q,
  			   struct videobuf_buffer *buf)
  {
  	struct videobuf_dma_sg_memory *mem = buf->priv;
  	BUG_ON(!mem || !mem->dma.sglen);
  
  	MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
  	MAGIC_CHECK(mem->dma.magic, MAGIC_DMABUF);
  
  	dma_sync_sg_for_cpu(q->dev, mem->dma.sglist,
  			    mem->dma.nr_pages, mem->dma.direction);
  
  	return 0;
  }
  
  static int __videobuf_mmap_mapper(struct videobuf_queue *q,
  				  struct videobuf_buffer *buf,
  				  struct vm_area_struct *vma)
  {
  	struct videobuf_dma_sg_memory *mem = buf->priv;
  	struct videobuf_mapping *map;
  	unsigned int first, last, size = 0, i;
  	int retval;
  
  	retval = -EINVAL;
  
  	BUG_ON(!mem);
  	MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
  
  	/* look for first buffer to map */
  	for (first = 0; first < VIDEO_MAX_FRAME; first++) {
  		if (buf == q->bufs[first]) {
  			size = PAGE_ALIGN(q->bufs[first]->bsize);
  			break;
  		}
  	}
  
  	/* paranoia, should never happen since buf is always valid. */
  	if (!size) {
  		dprintk(1, "mmap app bug: offset invalid [offset=0x%lx]\n",
  				(vma->vm_pgoff << PAGE_SHIFT));
  		goto done;
  	}
  
  	last = first;
  
  	/* create mapping + update buffer list */
  	retval = -ENOMEM;
  	map = kmalloc(sizeof(struct videobuf_mapping), GFP_KERNEL);
  	if (NULL == map)
  		goto done;
  
  	size = 0;
  	for (i = first; i <= last; i++) {
  		if (NULL == q->bufs[i])
  			continue;
  		q->bufs[i]->map   = map;
  		q->bufs[i]->baddr = vma->vm_start + size;
  		size += PAGE_ALIGN(q->bufs[i]->bsize);
  	}
  
  	map->count    = 1;
  	map->q        = q;
  	vma->vm_ops   = &videobuf_vm_ops;
  	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
  	vma->vm_flags &= ~VM_IO; /* using shared anonymous pages */
  	vma->vm_private_data = map;
  	dprintk(1, "mmap %p: q=%p %08lx-%08lx pgoff %08lx bufs %d-%d\n",
  		map, q, vma->vm_start, vma->vm_end, vma->vm_pgoff, first, last);
  	retval = 0;
  
  done:
  	return retval;
  }
  
  static struct videobuf_qtype_ops sg_ops = {
  	.magic        = MAGIC_QTYPE_OPS,
  
  	.alloc_vb     = __videobuf_alloc_vb,
  	.iolock       = __videobuf_iolock,
  	.sync         = __videobuf_sync,
  	.mmap_mapper  = __videobuf_mmap_mapper,
  	.vaddr        = __videobuf_to_vaddr,
  };
  
  void *videobuf_sg_alloc(size_t size)
  {
  	struct videobuf_queue q;
  
  	/* Required to make generic handler to call __videobuf_alloc */
  	q.int_ops = &sg_ops;
  
  	q.msize = size;
  
  	return videobuf_alloc_vb(&q);
  }
  EXPORT_SYMBOL_GPL(videobuf_sg_alloc);
  
  void videobuf_queue_sg_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, &sg_ops, ext_lock);
  }
  EXPORT_SYMBOL_GPL(videobuf_queue_sg_init);
  
  