From: Tomasz Figa <tfiga@chromium.org>
To: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>,
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: [PATCHv2 8/8] videobuf2: handle non-contiguous DMA allocations
Date: Wed, 7 Jul 2021 23:10:37 +0900 [thread overview]
Message-ID: <CAAFQd5DDpxXBb=eJpzLPOhGQAgtBKnn0aTo=3Vs-rf44cu8OQA@mail.gmail.com> (raw)
In-Reply-To: <YOWsNa0Zaf9UuGWH@google.com>
On Wed, Jul 7, 2021 at 10:29 PM Sergey Senozhatsky
<senozhatsky@chromium.org> wrote:
>
> On (21/07/07 21:48), Tomasz Figa wrote:
> > > [..]
> > > > static void *vb2_dc_vaddr(struct vb2_buffer *vb, void *buf_priv)
> > > > {
> > > > struct vb2_dc_buf *buf = buf_priv;
> > > >
> > > > 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;
> > > > }
> > > >
> > > > And in vb2_dc_alloc functions set vaddr for !DMA_ATTR_NO_KERNEL_MAPPING
> > > > in both coherent and non-coherent. So that we probably can have less
> > > > branches when ->vaddr is NULL for one type of allocations, and is not
> > > > NULL for another.
> >
> > I'd prefer if it stayed as is. This opportunistic mapping as in the
> > current revision is quite nice, because most of the drivers don't
> > bother to set DMA_ATTR_NO_KERNEL_MAPPING even if they don't need the
> > kernel mapping. Also, even if the driver itself doesn't need the
> > kernel mapping, we can still create one on demand if the DMA-buf
> > importer demands it from us.
>
> [..]
>
> > > > static int vb2_dc_alloc_coherent(struct vb2_dc_buf *buf)
> > > > {
> > > > struct vb2_queue *q = buf->vb->vb2_queue;
> > > >
> > > > buf->cookie = dma_alloc_attrs(buf->dev,
> > > > buf->size,
> > > > &buf->dma_addr,
> > > > GFP_KERNEL | q->gfp_flags,
> > > > buf->attrs);
> > > > if (!buf->cookie)
> > > > return -ENOMEM;
> > > >
> > > > if (q->dma_attrs & DMA_ATTR_NO_KERNEL_MAPPING)
> > > > return 0;
> > > >
> > > > buf->vaddr = buf->cookie;
> > > > return 0;
> > > > }
> > > >
> > > > static int vb2_dc_alloc_non_coherent(struct vb2_dc_buf *buf)
> > > > {
> > > > struct vb2_queue *q = buf->vb->vb2_queue;
> > > >
> > > > buf->dma_sgt = dma_alloc_noncontiguous(buf->dev,
> > > > buf->size,
> > > > buf->dma_dir,
> > > > GFP_KERNEL | q->gfp_flags,
> > > > buf->attrs);
> > > > if (!buf->dma_sgt)
> > > > return -ENOMEM;
> > > >
> > > > if (q->dma_attrs & DMA_ATTR_NO_KERNEL_MAPPING)
> > > > return 0;
> > > >
> > > > buf->vaddr = dma_vmap_noncontiguous(buf->dev, buf->size, buf->dma_sgt);
> > > > if (!buf->vaddr) {
> > > > dma_free_noncontiguous(buf->dev, buf->size,
> > > > buf->dma_sgt, buf->dma_addr);
> > > > return -ENOMEM;
> > > > }
> > > > return 0;
> > > > }
> > >
> > > I guess this should address the case when
> > >
> > > "after allocating the buffer, the buffer is exported as a dma_buf and
> > > another device calls dma_buf_ops vb2_dc_dmabuf_ops_vmap, which in turn
> > > calls dma_buf_map_set_vaddr(map, buf->vaddr); with a NULL buf->vaddr"
> >
> > Sorry, I fail to get what this is about. Where does this quote come from?
>
> Bottom half of https://lore.kernel.org/lkml/10a0903a-e295-5cba-683a-1eb89a0804ed@xs4all.nl/
I see, thanks for the pointer. Yes, vb2_dc_dmabuf_ops_vmap() needs to
be changed so that it calls vb2_dc_vaddr() internally instead of
relying on buf->vaddr directly.
next prev parent reply other threads:[~2021-07-07 14:10 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-27 13:13 [PATCHv2 0/8] videobuf2: support new noncontiguous DMA API Sergey Senozhatsky
2021-04-27 13:13 ` [PATCHv2 1/8] videobuf2: rework vb2_mem_ops API Sergey Senozhatsky
2021-04-27 13:13 ` [PATCHv2 2/8] videobuf2: inverse buffer cache_hints flags Sergey Senozhatsky
2021-04-27 13:13 ` [PATCHv2 3/8] videobuf2: split buffer cache_hints initialisation Sergey Senozhatsky
2021-04-27 13:13 ` [PATCHv2 4/8] videobuf2: move cache_hints handling to allocators Sergey Senozhatsky
2021-04-27 13:13 ` [PATCHv2 5/8] videobuf2: add V4L2_MEMORY_FLAG_NON_COHERENT flag Sergey Senozhatsky
2021-04-27 13:13 ` [PATCHv2 6/8] videobuf2: add queue memory coherency parameter Sergey Senozhatsky
2021-04-27 13:13 ` [PATCHv2 7/8] videobuf2: handle V4L2_MEMORY_FLAG_NON_COHERENT flag Sergey Senozhatsky
2021-05-01 3:48 ` Sergey Senozhatsky
2021-06-03 11:32 ` Hans Verkuil
2021-06-17 1:46 ` Sergey Senozhatsky
2021-04-27 13:13 ` [PATCHv2 8/8] videobuf2: handle non-contiguous DMA allocations Sergey Senozhatsky
2021-04-28 6:14 ` Christoph Hellwig
2021-06-03 11:59 ` Hans Verkuil
2021-06-17 7:56 ` Sergey Senozhatsky
2021-06-17 8:01 ` Christoph Hellwig
2021-06-17 8:30 ` Tomasz Figa
2021-06-17 8:52 ` Christoph Hellwig
2021-06-17 9:40 ` Tomasz Figa
2021-06-17 10:06 ` Christoph Hellwig
2021-06-18 3:21 ` Tomasz Figa
2021-06-18 4:25 ` Christoph Hellwig
2021-06-18 4:44 ` Tomasz Figa
2021-06-22 7:33 ` Christoph Hellwig
2021-07-07 12:42 ` Tomasz Figa
2021-06-25 3:10 ` Sergey Senozhatsky
2021-07-07 12:48 ` Tomasz Figa
2021-07-07 13:29 ` Sergey Senozhatsky
2021-07-07 14:10 ` Tomasz Figa [this message]
2021-07-09 7:20 ` Sergey Senozhatsky
2021-06-17 7:56 ` Sergey Senozhatsky
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAAFQd5DDpxXBb=eJpzLPOhGQAgtBKnn0aTo=3Vs-rf44cu8OQA@mail.gmail.com' \
--to=tfiga@chromium.org \
--cc=hch@lst.de \
--cc=hverkuil-cisco@xs4all.nl \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=mchehab@kernel.org \
--cc=ribalda@chromium.org \
--cc=senozhatsky@chromium.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).