?Hi Randy,
On Mon, Aug 1, 2022 at 5:21 AM <ayaka@xxxxxxxxxxx> wrote:
>
> From: Randy Li <ayaka@xxxxxxxxxxx>
>
> This module is still at a early stage, I wrote this for showing what
> APIs we need here.
>
> Let me explain why we need such a module here.
> If you won't allocate buffers from a V4L2 M2M device, this module
> may not be very useful. I am sure the most of users won't know a
> device would require them allocate buffers from a DMA-Heap then
> import those buffers into a V4L2's queue.
>
> Then the question goes back to why DMA-Heap. From the Android's
> description, we know it is about the copyright's DRM.
> When we allocate a buffer in a DMA-Heap, it may register that buffer
> in the trusted execution environment so the firmware which is running
> or could only be acccesed from there could use that buffer later.
>
> The answer above leads to another thing which is not done in this
> version, the DMA mapping. Although in some platforms, a DMA-Heap
> responses a IOMMU device as well. For the genernal purpose, we would
> be better assuming the device mapping should be done for each device
> itself. The problem here we only know alloc_devs in those DMAbuf
> methods, which are DMA-heaps in my design, the device from the queue
> is not enough, a plane may requests another IOMMU device or table
> for mapping.
>
> Signed-off-by: Randy Li <ayaka@xxxxxxxxxxx>
> ---
> drivers/media/common/videobuf2/Kconfig | 6 +
> drivers/media/common/videobuf2/Makefile | 1 +
> .../common/videobuf2/videobuf2-dma-heap.c | 350 ++++++++++++++++++
> include/media/videobuf2-dma-heap.h | 30 ++
> 4 files changed, 387 insertions(+)
> create mode 100644 drivers/media/common/videobuf2/videobuf2-dma-heap.c
> create mode 100644 include/media/videobuf2-dma-heap.h
>
First of all, thanks for the series.
Possibly a stupid question, but why not just allocate the DMA-bufs
directly from the DMA-buf heap device in the userspace and just import
the buffers to the V4L2 device using V4L2_MEMORY_DMABUF?
Best regards,
Tomasz
> diff --git a/drivers/media/common/videobuf2/Kconfig b/drivers/media/common/videobuf2/Kconfig
> index d2223a12c95f..02235077f07e 100644
> --- a/drivers/media/common/videobuf2/Kconfig
> +++ b/drivers/media/common/videobuf2/Kconfig
> @@ -30,3 +30,9 @@ config VIDEOBUF2_DMA_SG
> config VIDEOBUF2_DVB
> tristate
> select VIDEOBUF2_CORE
> +
> +config VIDEOBUF2_DMA_HEAP
> + tristate
> + select VIDEOBUF2_CORE
> + select VIDEOBUF2_MEMOPS
> + select DMABUF_HEAPS
> diff --git a/drivers/media/common/videobuf2/Makefile b/drivers/media/common/videobuf2/Makefile
> index a6fe3f304685..7fe65f93117f 100644
> --- a/drivers/media/common/videobuf2/Makefile
> +++ b/drivers/media/common/videobuf2/Makefile
> @@ -10,6 +10,7 @@ endif
> # (e. g. LC_ALL=C sort Makefile)
> obj-$(CONFIG_VIDEOBUF2_CORE) += videobuf2-common.o
> obj-$(CONFIG_VIDEOBUF2_DMA_CONTIG) += videobuf2-dma-contig.o
> +obj-$(CONFIG_VIDEOBUF2_DMA_HEAP) += videobuf2-dma-heap.o
> obj-$(CONFIG_VIDEOBUF2_DMA_SG) += videobuf2-dma-sg.o
> obj-$(CONFIG_VIDEOBUF2_DVB) += videobuf2-dvb.o
> obj-$(CONFIG_VIDEOBUF2_MEMOPS) += videobuf2-memops.o
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-heap.c b/drivers/media/common/videobuf2/videobuf2-dma-heap.c
> new file mode 100644
> index 000000000000..377b82ab8f5a
> --- /dev/null
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-heap.c
> @@ -0,0 +1,350 @@
> +/*
> + * Copyright (C) 2022 Randy Li <ayaka@xxxxxxxxxxx>
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * 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.
> + *
> + */
> +
> +#include <linux/dma-buf.h>
> +#include <linux/dma-heap.h>
> +#include <linux/refcount.h>
> +#include <linux/scatterlist.h>
> +#include <linux/sched.h>
> +#include <linux/slab.h>
> +#include <linux/dma-mapping.h>
> +
> +#include <media/videobuf2-v4l2.h>
> +#include <media/videobuf2-memops.h>
> +#include <media/videobuf2-dma-heap.h>
> +
> +struct vb2_dmaheap_buf {
> + struct device *dev;
> + void *vaddr;
> + unsigned long size;
> + struct dma_buf *dmabuf;
> + dma_addr_t dma_addr;
> + unsigned long attrs;
> + enum dma_data_direction dma_dir;
> + struct sg_table *dma_sgt;
> +
> + /* MMAP related */
> + struct vb2_vmarea_handler handler;
> + refcount_t refcount;
> +
> + /* DMABUF related */
> + struct dma_buf_attachment *db_attach;
> +};
> +
> +/*********************************************/
> +/* callbacks for all buffers */
> +/*********************************************/
> +
> +void *vb2_dmaheap_cookie(struct vb2_buffer *vb, void *buf_priv)
> +{
> + struct vb2_dmaheap_buf *buf = buf_priv;
> +
> + return &buf->dma_addr;
> +}
> +
> +static void *vb2_dmaheap_vaddr(struct vb2_buffer *vb, void *buf_priv)
> +{
> + struct vb2_dmaheap_buf *buf = buf_priv;
> + struct iosys_map map;
> +
> + if (buf->vaddr)
> + return buf->vaddr;
> +
> + if (buf->db_attach) {
> + if (!dma_buf_vmap(buf->db_attach->dmabuf, &map))
> + buf->vaddr = map.vaddr;
> + }
> +
> + return buf->vaddr;
> +}
> +
> +static unsigned int vb2_dmaheap_num_users(void *buf_priv)
> +{
> + struct vb2_dmaheap_buf *buf = buf_priv;
> +
> + return refcount_read(&buf->refcount);
> +}
> +
> +static void vb2_dmaheap_prepare(void *buf_priv)
> +{
> + struct vb2_dmaheap_buf *buf = buf_priv;
> +
> + /* TODO: DMABUF exporter will flush the cache for us */
> + if (buf->db_attach)
> + return;
> +
> + dma_buf_end_cpu_access(buf->dmabuf, buf->dma_dir);
> +}
> +
> +static void vb2_dmaheap_finish(void *buf_priv)
> +{
> + struct vb2_dmaheap_buf *buf = buf_priv;
> +
> + /* TODO: DMABUF exporter will flush the cache for us */
> + if (buf->db_attach)
> + return;
> +
> + dma_buf_begin_cpu_access(buf->dmabuf, buf->dma_dir);
> +}
> +
> +/*********************************************/
> +/* callbacks for MMAP buffers */
> +/*********************************************/
> +
> +void vb2_dmaheap_put(void *buf_priv)
> +{
> + struct vb2_dmaheap_buf *buf = buf_priv;
> +
> + if (!refcount_dec_and_test(&buf->refcount))
> + return;
> +
> + dma_buf_put(buf->dmabuf);
> +
> + put_device(buf->dev);
> + kfree(buf);
> +}
> +
> +static void *vb2_dmaheap_alloc(struct vb2_buffer *vb,
> + struct device *dev,
> + unsigned long size)
> +{
> + struct vb2_queue *q = vb->vb2_queue;
> + struct dma_heap *heap;
> + struct vb2_dmaheap_buf *buf;
> + const char *heap_name;
> + int ret;
> +
> + if (WARN_ON(!dev))
> + return ERR_PTR(-EINVAL);
> +
> + heap_name = dev_name(dev);
> + if (!heap_name)
> + return ERR_PTR(-EINVAL);
> +
> + heap = dma_heap_find(heap_name);
> + if (!heap) {
> + dev_err(dev, "is not a DMA-heap device\n");
> + return ERR_PTR(-EINVAL);
> + }
> +
> + buf = kzalloc(sizeof *buf, GFP_KERNEL);
> + if (!buf)
> + return ERR_PTR(-ENOMEM);
> +
> + /* Prevent the device from being released while the buffer is used */
> + buf->dev = get_device(dev);
> + buf->attrs = vb->vb2_queue->dma_attrs;
> + buf->dma_dir = vb->vb2_queue->dma_dir;
> +
> + /* TODO: heap flags */
> + ret = dma_heap_buffer_alloc(heap, size, 0, 0);
> + if (ret < 0) {
> + dev_err(dev, "is not a DMA-heap device\n");
> + put_device(buf->dev);
> + kfree(buf);
> + return ERR_PTR(ret);
> + }
> + buf->dmabuf = dma_buf_get(ret);
> +
> + /* FIXME */
> + buf->dma_addr = 0;
> +
> + if ((q->dma_attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0)
> + buf->vaddr = buf->dmabuf;
> +
> + buf->handler.refcount = &buf->refcount;
> + buf->handler.put = vb2_dmaheap_put;
> + buf->handler.arg = buf;
> +
> + refcount_set(&buf->refcount, 1);
> +
> + return buf;
> +}
> +
> +static int vb2_dmaheap_mmap(void *buf_priv, struct vm_area_struct *vma)
> +{
> + struct vb2_dmaheap_buf *buf = buf_priv;
> + int ret;
> +
> + if (!buf) {
> + printk(KERN_ERR "No buffer to map\n");
> + return -EINVAL;
> + }
> +
> + vma->vm_flags &= ~VM_PFNMAP;
> +
> + ret = dma_buf_mmap(buf->dmabuf, vma, 0);
> + if (ret) {
> + pr_err("Remapping memory failed, error: %d\n", ret);
> + return ret;
> + }
> + vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
> + vma->vm_private_data = &buf->handler;
> + vma->vm_ops = &vb2_common_vm_ops;
> +
> + vma->vm_ops->open(vma);
> +
> + pr_debug("%s: mapped memid 0x%08lx at 0x%08lx, size %ld\n",
> + __func__, (unsigned long)buf->dma_addr, vma->vm_start,
> + buf->size);
> +
> + return 0;
> +}
> +
> +/*********************************************/
> +/* DMABUF ops for exporters */
> +/*********************************************/
> +
> +static struct dma_buf *vb2_dmaheap_get_dmabuf(struct vb2_buffer *vb,
> + void *buf_priv,
> + unsigned long flags)
> +{
> + struct vb2_dmaheap_buf *buf = buf_priv;
> + struct dma_buf *dbuf;
> +
> + dbuf = buf->dmabuf;
> +
> + return dbuf;
> +}
> +
> +/*********************************************/
> +/* callbacks for DMABUF buffers */
> +/*********************************************/
> +
> +static int vb2_dmaheap_map_dmabuf(void *mem_priv)
> +{
> + struct vb2_dmaheap_buf *buf = mem_priv;
> + struct sg_table *sgt;
> +
> + if (WARN_ON(!buf->db_attach)) {
> + pr_err("trying to pin a non attached buffer\n");
> + return -EINVAL;
> + }
> +
> + if (WARN_ON(buf->dma_sgt)) {
> + pr_err("dmabuf buffer is already pinned\n");
> + return 0;
> + }
> +
> + /* get the associated scatterlist for this buffer */
> + sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
> + if (IS_ERR(sgt)) {
> + pr_err("Error getting dmabuf scatterlist\n");
> + return -EINVAL;
> + }
> +
> + buf->dma_addr = sg_dma_address(sgt->sgl);
> + buf->dma_sgt = sgt;
> + buf->vaddr = NULL;
> +
> + return 0;
> +}
> +
> +static void vb2_dmaheap_unmap_dmabuf(void *mem_priv)
> +{
> + struct vb2_dmaheap_buf *buf = mem_priv;
> + struct sg_table *sgt = buf->dma_sgt;
> + struct iosys_map map = IOSYS_MAP_INIT_VADDR(buf->vaddr);
> +
> + if (WARN_ON(!buf->db_attach)) {
> + pr_err("trying to unpin a not attached buffer\n");
> + return;
> + }
> +
> + if (WARN_ON(!sgt)) {
> + pr_err("dmabuf buffer is already unpinned\n");
> + return;
> + }
> +
> + if (buf->vaddr) {
> + dma_buf_vunmap(buf->db_attach->dmabuf, &map);
> + buf->vaddr = NULL;
> + }
> + dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
> +
> + buf->dma_addr = 0;
> + buf->dma_sgt = NULL;
> +}
> +
> +static void vb2_dmaheap_detach_dmabuf(void *mem_priv)
> +{
> + struct vb2_dmaheap_buf *buf = mem_priv;
> +
> + /* if vb2 works correctly you should never detach mapped buffer */
> + if (WARN_ON(buf->dma_addr))
> + vb2_dmaheap_unmap_dmabuf(buf);
> +
> + /* detach this attachment */
> + dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach);
> + kfree(buf);
> +}
> +
> +static void *vb2_dmaheap_attach_dmabuf(struct vb2_buffer *vb, struct device *dev,
> + struct dma_buf *dbuf, unsigned long size)
> +{
> + struct vb2_dmaheap_buf *buf;
> + struct dma_buf_attachment *dba;
> +
> + if (dbuf->size < size)
> + return ERR_PTR(-EFAULT);
> +
> + if (WARN_ON(!dev))
> + return ERR_PTR(-EINVAL);
> + /*
> + * TODO: A better way to check whether the buffer is coming
> + * from this heap or this heap could accept this buffer
> + */
> + if (strcmp(dbuf->exp_name, dev_name(dev)))
> + return ERR_PTR(-EINVAL);
> +
> + buf = kzalloc(sizeof(*buf), GFP_KERNEL);
> + if (!buf)
> + return ERR_PTR(-ENOMEM);
> +
> + buf->dev = dev;
> + /* create attachment for the dmabuf with the user device */
> + dba = dma_buf_attach(dbuf, buf->dev);
> + if (IS_ERR(dba)) {
> + pr_err("failed to attach dmabuf\n");
> + kfree(buf);
> + return dba;
> + }
> +
> + buf->dma_dir = vb->vb2_queue->dma_dir;
> + buf->size = size;
> + buf->db_attach = dba;
> +
> + return buf;
> +}
> +
> +const struct vb2_mem_ops vb2_dmaheap_memops = {
> + .alloc = vb2_dmaheap_alloc,
> + .put = vb2_dmaheap_put,
> + .get_dmabuf = vb2_dmaheap_get_dmabuf,
> + .cookie = vb2_dmaheap_cookie,
> + .vaddr = vb2_dmaheap_vaddr,
> + .prepare = vb2_dmaheap_prepare,
> + .finish = vb2_dmaheap_finish,
> + .map_dmabuf = vb2_dmaheap_map_dmabuf,
> + .unmap_dmabuf = vb2_dmaheap_unmap_dmabuf,
> + .attach_dmabuf = vb2_dmaheap_attach_dmabuf,
> + .detach_dmabuf = vb2_dmaheap_detach_dmabuf,
> + .num_users = vb2_dmaheap_num_users,
> + .mmap = vb2_dmaheap_mmap,
> +};
> +
> +MODULE_DESCRIPTION("DMA-Heap memory handling routines for videobuf2");
> +MODULE_AUTHOR("Randy Li <ayaka@xxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");
> +MODULE_IMPORT_NS(DMA_BUF);
> diff --git a/include/media/videobuf2-dma-heap.h b/include/media/videobuf2-dma-heap.h
> new file mode 100644
> index 000000000000..fa057f67d6e9
> --- /dev/null
> +++ b/include/media/videobuf2-dma-heap.h
> @@ -0,0 +1,30 @@
> +/*
> + * Copyright (C) 2022 Randy Li <ayaka@xxxxxxxxxxx>
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * 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.
> + *
> + */
> +
> +#ifndef _MEDIA_VIDEOBUF2_DMA_HEAP_H
> +#define _MEDIA_VIDEOBUF2_DMA_HEAP_H
> +
> +#include <media/videobuf2-v4l2.h>
> +#include <linux/dma-mapping.h>
> +
> +static inline dma_addr_t
> +vb2_dmaheap_plane_dma_addr(struct vb2_buffer *vb, unsigned int plane_no)
> +{
> + dma_addr_t *addr = vb2_plane_cookie(vb, plane_no);
> +
> + return *addr;
> +}
> +
> +extern const struct vb2_mem_ops vb2_dmaheap_memops;
> +#endif
> --
> 2.17.1
>
