From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
Tomasz Figa <tfiga@chromium.org>,
Dafna Hirschfeld <dafna.hirschfeld@collabora.com>,
Ricardo Ribalda <ribalda@chromium.org>,
Christoph Hellwig <hch@lst.de>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv4 8/8] videobuf2: handle non-contiguous DMA allocations
Date: Tue, 17 Aug 2021 20:56:59 +0900 [thread overview]
Message-ID: <YRukCziknzz/3/sV@google.com> (raw)
In-Reply-To: <fd1e8bbe-4cbe-9586-7c8f-0896af043d4a@xs4all.nl>
Hi,
On (21/08/03 12:15), Hans Verkuil wrote:
> > static void *vb2_dc_vaddr(struct vb2_buffer *vb, void *buf_priv)
> > {
> > struct vb2_dc_buf *buf = buf_priv;
> > - struct dma_buf_map map;
> > - int ret;
> >
> > - if (!buf->vaddr && buf->db_attach) {
> > - ret = dma_buf_vmap(buf->db_attach->dmabuf, &map);
> > - buf->vaddr = ret ? NULL : map.vaddr;
> > + if (buf->vaddr)
> > + return buf->vaddr;
> > +
> > + if (buf->db_attach) {
> > + struct dma_buf_map map;
> > +
> > + if (!dma_buf_vmap(buf->db_attach->dmabuf, &map))
> > + buf->vaddr = map.vaddr;
> > +
> > + return buf->vaddr;
> > }
> >
> > + if (!buf->coherent_mem)
> > + buf->vaddr = dma_vmap_noncontiguous(buf->dev, buf->size,
> > + buf->dma_sgt);
> > return buf->vaddr;
> > }
>
> This function really needs a bunch of comments.
>
> What I want to see here specifically is under which circumstances this function
> can return NULL.
>
> - dma_buf_vmap returns an error
> - for non-coherent memory dma_vmap_noncontiguous returns an error
> - coherent memory with DMA_ATTR_NO_KERNEL_MAPPING set.
OK, I added some comments.
> In the latter case, if a buffer with coherent memory and DMA_ATTR_NO_KERNEL_MAPPING
> is exported as a dma_buf, and dma_buf_vmap is called by the importer of this dma-buf,
> what happens then? I think that in that case dma_buf_vmap should return an error?
Should we error out in vb2_dc_vaddr() in this case?
---
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index d4089d0b5ec5..e1d8ae1548fa 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -102,6 +102,9 @@ static void *vb2_dc_vaddr(struct vb2_buffer *vb, void *buf_priv)
if (buf->db_attach) {
struct dma_buf_map map;
+ if (WARN_ON(buf->attrs & DMA_ATTR_NO_KERNEL_MAPPING))
+ return NULL;
+
if (!dma_buf_vmap(buf->db_attach->dmabuf, &map))
buf->vaddr = map.vaddr;
---
[..]
> > @@ -362,7 +451,7 @@ static int vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf, struct dma_buf_map *map)
> > {
> > struct vb2_dc_buf *buf = dbuf->priv;
> >
> > - dma_buf_map_set_vaddr(map, buf->vaddr);
> > + dma_buf_map_set_vaddr(map, vb2_dc_vaddr(buf->vb, buf));
>
> vb2_dc_vaddr() can return NULL, shouldn't this function return an error in that case?
Done, thanks.
> BTW, looking at where vb2_plane_vaddr() is called in drivers I notice that most (all?)
> drivers do not check for NULL. Somewhat scary, to be honest. That's a separate issue, though.
I may have some time in the future and can add missing if-s to the
drivers.
next prev parent reply other threads:[~2021-08-17 11:57 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-27 7:05 [PATCHv4 0/8] videobuf2: support new noncontiguous DMA API Sergey Senozhatsky
2021-07-27 7:05 ` [PATCHv4 1/8] videobuf2: rework vb2_mem_ops API Sergey Senozhatsky
2021-08-03 8:08 ` Hans Verkuil
2021-08-17 10:41 ` Sergey Senozhatsky
2021-07-27 7:05 ` [PATCHv4 2/8] videobuf2: inverse buffer cache_hints flags Sergey Senozhatsky
2021-07-27 7:05 ` [PATCHv4 3/8] videobuf2: split buffer cache_hints initialisation Sergey Senozhatsky
2021-08-03 8:10 ` Hans Verkuil
2021-08-17 10:41 ` Sergey Senozhatsky
2021-07-27 7:05 ` [PATCHv4 4/8] videobuf2: move cache_hints handling to allocators Sergey Senozhatsky
2021-08-03 8:11 ` Hans Verkuil
2021-08-17 10:42 ` Sergey Senozhatsky
2021-07-27 7:05 ` [PATCHv4 5/8] videobuf2: add V4L2_MEMORY_FLAG_NON_COHERENT flag Sergey Senozhatsky
2021-08-03 8:12 ` Hans Verkuil
2021-08-17 10:42 ` Sergey Senozhatsky
2021-07-27 7:05 ` [PATCHv4 6/8] videobuf2: add queue memory coherency parameter Sergey Senozhatsky
2021-08-03 8:29 ` Hans Verkuil
2021-08-17 10:43 ` Sergey Senozhatsky
2021-07-27 7:05 ` [PATCHv4 7/8] videobuf2: handle V4L2_MEMORY_FLAG_NON_COHERENT flag Sergey Senozhatsky
2021-08-03 8:31 ` Hans Verkuil
2021-08-17 10:43 ` Sergey Senozhatsky
2021-07-27 7:05 ` [PATCHv4 8/8] videobuf2: handle non-contiguous DMA allocations Sergey Senozhatsky
2021-08-03 8:33 ` Hans Verkuil
2021-08-03 8:39 ` Hans Verkuil
2021-08-23 10:28 ` Sergey Senozhatsky
2021-08-23 10:27 ` Sergey Senozhatsky
2021-08-03 10:15 ` Hans Verkuil
2021-08-17 11:56 ` Sergey Senozhatsky [this message]
2021-08-18 9:20 ` Tomasz Figa
2021-08-23 10:29 ` Sergey Senozhatsky
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