From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To: Hans de Goede <hdegoede@redhat.com>
Cc: "Sumit Semwal" <sumit.semwal@linaro.org>,
"Benjamin Gaignard" <benjamin.gaignard@collabora.com>,
"Brian Starkey" <Brian.Starkey@arm.com>,
"John Stultz" <jstultz@google.com>,
"T.J. Mercier" <tjmercier@google.com>,
"Christian König" <christian.koenig@amd.com>,
"Lennart Poettering" <mzxreary@0pointer.de>,
"Robert Mader" <robert.mader@collabora.com>,
"Sebastien Bacher" <sebastien.bacher@canonical.com>,
"Linux Media Mailing List" <linux-media@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
linaro-mm-sig@lists.linaro.org,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Bryan O'Donoghue" <bryan.odonoghue@linaro.org>,
"Milan Zamazal" <mzamazal@redhat.com>,
"Maxime Ripard" <mripard@redhat.com>,
"Andrey Konovalov" <andrey.konovalov.ynk@gmail.com>
Subject: Re: Safety of opening up /dev/dma_heap/* to physically present users (udev uaccess tag) ?
Date: Tue, 7 May 2024 18:09:13 +0300 [thread overview]
Message-ID: <e7ilwp3vc32xze3iu2ejgqlgz44codsktnvyiufjhuf2zxcnnf@tnwzgzoxvbg2> (raw)
In-Reply-To: <3c0c7e7e-1530-411b-b7a4-9f13e0ff1f9e@redhat.com>
On Tue, May 07, 2024 at 04:34:24PM +0200, Hans de Goede wrote:
> Hi Dmitry,
>
> On 5/7/24 3:32 PM, Dmitry Baryshkov wrote:
> > On Mon, May 06, 2024 at 01:49:17PM +0200, Hans de Goede wrote:
> >> Hi dma-buf maintainers, et.al.,
> >>
> >> Various people have been working on making complex/MIPI cameras work OOTB
> >> with mainline Linux kernels and an opensource userspace stack.
> >>
> >> The generic solution adds a software ISP (for Debayering and 3A) to
> >> libcamera. Libcamera's API guarantees that buffers handed to applications
> >> using it are dma-bufs so that these can be passed to e.g. a video encoder.
> >>
> >> In order to meet this API guarantee the libcamera software ISP allocates
> >> dma-bufs from userspace through one of the /dev/dma_heap/* heaps. For
> >> the Fedora COPR repo for the PoC of this:
> >> https://hansdegoede.dreamwidth.org/28153.html
> >
> > Is there any reason for allocating DMA buffers for libcamera through
> > /dev/dma_heap/ rather than allocating them via corresponding media
> > device and then giving them away to DRM / VPU / etc?
> >
> > At least this should solve the permission usecase: if the app can open
> > camera device, it can allocate a buffer.
>
> This is with a software ISP, the input buffers with raw bayer data
> come from a v4l2 device, but the output buffers with the processed
> data are purely userspace managed in this case.
Ah, I see. Then why do you require the DMA-ble buffer at all? If you are
providing data to VPU or DRM, then you should be able to get the buffer
from the data-consuming device. If the data is further processed by
a userspace app, then it should not require DMA memory at all.
My main concern is that dma-heaps is both too generic and too limiting
for the generic library implementation.
--
With best wishes
Dmitry
next prev parent reply other threads:[~2024-05-07 15:09 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-06 11:49 Safety of opening up /dev/dma_heap/* to physically present users (udev uaccess tag) ? Hans de Goede
2024-05-06 12:05 ` Maxime Ripard
2024-05-06 12:11 ` Hans de Goede
2024-05-06 13:38 ` Daniel Vetter
2024-05-06 14:01 ` Hans de Goede
2024-05-07 11:15 ` Daniel Vetter
2024-05-08 5:46 ` Daniel Stone
2024-05-08 8:33 ` Daniel Vetter
2024-05-08 8:38 ` Daniel Stone
2024-05-08 15:49 ` Daniel Vetter
2024-05-09 9:23 ` Daniel Stone
2024-05-16 10:18 ` Daniel Vetter
2024-05-13 13:51 ` Simon Ser
2024-05-16 10:13 ` Daniel Vetter
2024-05-16 11:49 ` Christian König
2024-05-07 13:34 ` Dmitry Baryshkov
2024-05-07 18:59 ` Laurent Pinchart
2024-05-22 13:34 ` Maxime Ripard
2024-05-23 9:41 ` Daniel Vetter
2024-05-07 13:32 ` Dmitry Baryshkov
2024-05-07 14:34 ` Hans de Goede
2024-05-07 15:09 ` Dmitry Baryshkov [this message]
2024-05-07 15:15 ` Bryan O'Donoghue
2024-05-07 15:19 ` Dmitry Baryshkov
2024-05-07 18:40 ` Laurent Pinchart
2024-05-07 19:59 ` Dmitry Baryshkov
2024-05-07 20:15 ` Laurent Pinchart
2024-05-08 8:39 ` Daniel Vetter
2024-05-08 21:54 ` Laurent Pinchart
2024-05-13 8:39 ` Maxime Ripard
2024-05-07 17:36 ` Daniel Vetter
2024-05-07 18:36 ` Laurent Pinchart
2024-05-07 20:07 ` Nicolas Dufresne
2024-05-08 8:36 ` Daniel Vetter
2024-05-08 21:51 ` Laurent Pinchart
2024-05-08 21:52 ` Laurent Pinchart
2024-05-13 8:29 ` Maxime Ripard
2024-05-13 8:34 ` Laurent Pinchart
2024-05-13 15:10 ` Nicolas Dufresne
2024-05-14 20:42 ` Laurent Pinchart
2024-05-15 17:43 ` nicolas.dufresne
2024-05-16 11:27 ` Laurent Pinchart
2024-05-16 17:11 ` nicolas.dufresne
2024-05-21 8:43 ` Maxime Ripard
2024-05-21 14:18 ` nicolas.dufresne
2024-05-16 7:00 ` Simon Ser
2024-05-16 11:20 ` Laurent Pinchart
2024-05-22 13:02 ` Nicolas Dufresne
2024-05-13 13:42 ` Nicolas Dufresne
2024-05-13 13:51 ` Maxime Ripard
2024-05-13 15:06 ` Nicolas Dufresne
2024-05-14 20:45 ` Laurent Pinchart
2024-05-14 20:52 ` Nicolas Dufresne
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