From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Tomasz Figa <tfiga@chromium.org>
Cc: "Linux Media Mailing List" <linux-media@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Stanimir Varbanov" <stanimir.varbanov@linaro.org>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Hans Verkuil" <hverkuil@xs4all.nl>,
"Pawel Osciak" <posciak@chromium.org>,
"Alexandre Courbot" <acourbot@chromium.org>,
kamil@wypas.org, a.hajda@samsung.com,
"Kyungmin Park" <kyungmin.park@samsung.com>,
jtp.park@samsung.com, "Philipp Zabel" <p.zabel@pengutronix.de>,
"Tiffany Lin (林慧珊)" <tiffany.lin@mediatek.com>,
"Andrew-CT Chen (陳智迪)" <andrew-ct.chen@mediatek.com>,
todor.tomov@linaro.org, nicolas@ndufresne.ca,
"Paul Kocialkowski" <paul.kocialkowski@bootlin.com>,
dave.stevenson@raspberrypi.org,
"Ezequiel Garcia" <ezequiel@collabora.com>
Subject: Re: [PATCH 1/2] media: docs-rst: Document memory-to-memory video decoder interface
Date: Sun, 21 Oct 2018 12:26:26 +0300 [thread overview]
Message-ID: <2087236.RgOn5EXAKT@avalon> (raw)
In-Reply-To: <CAAFQd5D=Lj2XzUMK1LpOXbK3nTdNCFKRkfj3yfpV9mguDkcvdw@mail.gmail.com>
Hi Tomasz,
On Saturday, 20 October 2018 13:24:20 EEST Tomasz Figa wrote:
> On Thu, Oct 18, 2018 at 7:03 PM Tomasz Figa wrote:
> > On Wed, Oct 17, 2018 at 10:34 PM Laurent Pinchart wrote:
> >> Hi Tomasz,
> >>
> >> Thank you for the patch.
> >
> > Thanks for your comments! Please see my replies inline.
> >
> >> On Tuesday, 24 July 2018 17:06:20 EEST Tomasz Figa wrote:
>
> [snip]
>
> >>> +4. At this point, decoding is paused and the driver will accept, but
> >>> not
> >>> + process any newly queued ``OUTPUT`` buffers until the client
> >>> issues
> >>> + ``V4L2_DEC_CMD_START`` or restarts streaming on any queue.
> >>> +
> >>> +* Once the drain sequence is initiated, the client needs to drive it
> >>> to
> >>> + completion, as described by the above steps, unless it aborts the
> >>> process
> >>> + by issuing :c:func:`VIDIOC_STREAMOFF` on ``OUTPUT`` queue. The client
> >>> + is not allowed to issue ``V4L2_DEC_CMD_START`` or
> >>> ``V4L2_DEC_CMD_STOP``
> >>> + again while the drain sequence is in progress and they will fail with
> >>> + -EBUSY error code if attempted.
> >>
> >> While this seems OK to me, I think drivers will need help to implement
> >> all the corner cases correctly without race conditions.
> >
> > We went through the possible list of corner cases and concluded that
> > there is no use in handling them, especially considering how much they
> > would complicate both the userspace and the drivers. Not even
> > mentioning some hardware, like s5p-mfc, which actually has a dedicated
> > flush operation, that needs to complete before the decoder can switch
> > back to normal mode.
>
> Actually I misread your comment.
>
> Agreed that the decoder commands are a bit tricky to implement
> properly. That's one of the reasons I decided to make the return
> -EBUSY while an existing drain is in progress.
>
> Do you have any particular simplification in mind that could avoid
> some corner cases?
Not really on the spec side. I think we'll have to implement helper functions
for drivers to use if we want to ensure a consistent and bug-free behaviour.
--
Regards,
Laurent Pinchart
next prev parent reply other threads:[~2018-10-21 9:26 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-24 14:06 [PATCH 0/2] Document memory-to-memory video codec interfaces Tomasz Figa
2018-07-24 14:06 ` [PATCH 1/2] media: docs-rst: Document memory-to-memory video decoder interface Tomasz Figa
2018-07-25 11:58 ` Hans Verkuil
2018-07-26 10:20 ` Tomasz Figa
2018-07-26 10:36 ` Philipp Zabel
2018-08-07 6:55 ` Tomasz Figa
2018-07-26 10:57 ` Hans Verkuil
2018-08-07 7:05 ` Tomasz Figa
2018-08-07 7:37 ` Hans Verkuil
2018-08-08 2:55 ` Tomasz Figa
2018-08-21 11:29 ` Stanimir Varbanov
2018-08-27 4:09 ` Tomasz Figa
2018-10-15 10:13 ` Tomasz Figa
2018-10-16 1:09 ` Nicolas Dufresne
2018-08-07 7:13 ` Hans Verkuil
2018-08-07 19:11 ` Maxime Jourdan
2018-08-08 3:07 ` Tomasz Figa
2018-08-08 7:19 ` Maxime Jourdan
2018-08-08 3:11 ` Tomasz Figa
2018-08-08 6:43 ` Hans Verkuil
2018-08-08 6:54 ` Ian Arkver
2018-09-19 10:17 ` Tomasz Figa
2018-10-08 12:22 ` Hans Verkuil
2018-10-09 4:23 ` Tomasz Figa
2018-10-09 6:39 ` Hans Verkuil
2018-07-30 12:52 ` Hans Verkuil
2018-08-07 7:08 ` Tomasz Figa
2018-08-08 2:46 ` Tomasz Figa
2018-08-20 13:04 ` Philipp Zabel
2018-08-20 13:12 ` Tomasz Figa
2018-08-20 14:13 ` Philipp Zabel
2018-08-20 14:27 ` Tomasz Figa
2018-08-20 15:33 ` Philipp Zabel
2018-08-27 4:03 ` Tomasz Figa
2018-08-31 8:26 ` Alexandre Courbot
2018-09-05 5:45 ` Tomasz Figa
2018-10-17 13:34 ` Laurent Pinchart
2018-10-18 10:03 ` Tomasz Figa
2018-10-18 11:22 ` Laurent Pinchart
2018-10-20 8:52 ` Tomasz Figa
2018-10-21 9:23 ` Laurent Pinchart
2018-10-22 6:19 ` Tomasz Figa
2018-10-20 10:24 ` Tomasz Figa
2018-10-21 9:26 ` Laurent Pinchart [this message]
2018-10-20 15:39 ` Tomasz Figa
2018-07-24 14:06 ` [PATCH 2/2] media: docs-rst: Document memory-to-memory video encoder interface Tomasz Figa
2018-07-25 13:41 ` Philipp Zabel
2018-08-07 6:07 ` Tomasz Figa
2018-07-25 13:57 ` Hans Verkuil
2018-08-07 6:54 ` Tomasz Figa
2018-08-07 7:25 ` Hans Verkuil
2018-10-16 7:36 ` Tomasz Figa
2018-10-16 13:49 ` Hans Verkuil
2018-10-22 4:50 ` Tomasz Figa
2018-09-07 20:17 ` Ezequiel Garcia
2018-09-10 3:34 ` Tomasz Figa
2018-10-17 15:19 ` Laurent Pinchart
2018-10-22 6:12 ` Tomasz Figa
2018-07-25 13:28 ` [PATCH 0/2] Document memory-to-memory video codec interfaces Philipp Zabel
2018-07-25 13:35 ` Tomasz Figa
2018-09-10 9:13 ` Hans Verkuil
2018-09-11 3:52 ` Tomasz Figa
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