From: Keiichi Watanabe <keiichiw@chromium.org> To: Gerd Hoffmann <kraxel@redhat.com> Cc: virtio-dev@lists.oasis-open.org, "Linux Media Mailing List" <linux-media@vger.kernel.org>, "Alexandre Courbot" <acourbot@chromium.org>, "Alex Lau" <alexlau@chromium.org>, "Daniel Vetter" <daniel@ffwll.ch>, "Dylan Reid" <dgreid@chromium.org>, "David Staessens" <dstaessens@chromium.org>, "Dmitry Sepp" <dmitry.sepp@opensynergy.com>, "Enrico Granata" <egranata@google.com>, "Frediano Ziglio" <fziglio@redhat.com>, "Hans Verkuil" <hverkuil@xs4all.nl>, "Stéphane Marchesin" <marcheu@chromium.org>, "Pawel Osciak" <posciak@chromium.org>, spice-devel@lists.freedesktop.org, "David Stevens" <stevensd@chromium.org>, "Tomasz Figa" <tfiga@chromium.org>, uril@redhat.com, "Samiullah Khawaja" <samiullah.khawaja@opensynergy.com>, "Kiran Pawar" <kiran.pawar@opensynergy.com> Subject: Re: [PATCH v3 1/2] virtio-video: Add virtio video device specification Date: Thu, 27 Feb 2020 16:24:00 +0900 [thread overview] Message-ID: <CAD90VcaTJh5MTRggpOmCK2LAryMHha2+7nPkFVTT8N8S06tf-A@mail.gmail.com> (raw) In-Reply-To: <20200225095956.7rtwugfru4dbjj7q@sirius.home.kraxel.org> Thanks for the review, Gerd. Please see my replies inline below. FYI, I'm implementing virtio-video device for ChromeOS that works with Dmitry's virtio-video driver https://patchwork.linuxtv.org/patch/61717/. Once it becomes fully functional, I'll post a list of possible improvements of protocol. On Tue, Feb 25, 2020 at 7:00 PM Gerd Hoffmann <kraxel@redhat.com> wrote: > > On Thu, Feb 06, 2020 at 07:20:57PM +0900, Keiichi Watanabe wrote: > > From: Dmitry Sepp <dmitry.sepp@opensynergy.com> > > > > The virtio video encoder device and decoder device provide functionalities to > > encode and decode video stream respectively. > > Though video encoder and decoder are provided as different devices, they use a > > same protocol. > > > > Signed-off-by: Dmitry Sepp <dmitry.sepp@opensynergy.com> > > Signed-off-by: Keiichi Watanabe <keiichiw@chromium.org> > > Finally found the time for a closer look. > Pretty good overall, some minor nits below ... > > > +\begin{description} > > +\item[\field{version}] is the protocol version that the device talks. > > + The device MUST set this to 0. > > What is the intended use case for this? > > Given that virtio has feature flags to negotiate support for optional > features and protocol extensions between driver and device, why do you > think this is needed? While feature flags work well when we "extend" the protocol with an optional feature, they don't when we want to "drop" or "modify" features. For example, I guess it'd be useful when we want: * to abandon a non-optional command, * to change a non-optional struct's layout,or * to change the order of commands in which the device expects to be sent. Though it might be possible to handle these changes by feature flags, I suspect the version number allow us to transition protocols more smoothly. WDYT? > > > +The format description \field{virtio_video_format_desc} is defined as > > +follows: > > +\begin{lstlisting} > > +enum virtio_video_format { > > + /* Raw formats */ > > + VIRTIO_VIDEO_FORMAT_RAW_MIN = 1, > > + VIRTIO_VIDEO_FORMAT_ARGB8888 = VIRTIO_VIDEO_FORMAT_RAW_MIN, > > + VIRTIO_VIDEO_FORMAT_BGRA8888, > > + VIRTIO_VIDEO_FORMAT_NV12, /* 12 Y/CbCr 4:2:0 */ > > + VIRTIO_VIDEO_FORMAT_YUV420, /* 12 YUV 4:2:0 */ > > + VIRTIO_VIDEO_FORMAT_YVU420, /* 12 YVU 4:2:0 */ > > + VIRTIO_VIDEO_FORMAT_RAW_MAX = VIRTIO_VIDEO_FORMAT_YVU420, > > I'm wondering what the *_MIN and *_MAX values here (and elsewhere) are > good for? I doubt drivers would actually loop over formats from min to > max, I'd expect they check for specific formats they can handle instead. > > If you want define the range for valid raw formats I'd suggest to leave > some room, so new formats can be added without changing MAX values, i.e. > use -- for example -- RAW_MIN = 0x100, RAW_MAX = 0x1ff, CODED_MIN=0x200, > CODED_MAX=0x2ff. Or just drop them ... Ah, that's a good point. I agree that drivers don't need to loop over formats. If they need, they can define such an alias locally. Still, I guess it's worth defining the range for valid raw/coded formats. This allows devices to report more detailed errors if a driver sent an unexpected format. i.e. "opposite format type" v.s. "unknown format" So, I'd use your idea of RAW_MIN = 0x100 and RAW_MAX = 0x1ff. > > > +struct virtio_video_query_control_level { > > + le32 profile; /* One of VIRTIO_VIDEO_PROFILE_* */ > ^^^^^^^ LEVEL ? Nope, it should be profile. This "profile" field is specified by the driver to query supported levels for a specific profile. In my understanding, supported levels depend on profiles. At least, the specification of H.264 [1] says that `"levels" are specified within each profile.` at section "0.5 Profiles and levels". [1] https://www.itu.int/rec/T-REC-H.264-201906-I/en Best regards, Keiichi > > cheers, > Gerd >
WARNING: multiple messages have this Message-ID (diff)
From: Keiichi Watanabe <keiichiw@chromium.org> To: Gerd Hoffmann <kraxel@redhat.com> Cc: virtio-dev@lists.oasis-open.org, "Linux Media Mailing List" <linux-media@vger.kernel.org>, "Alexandre Courbot" <acourbot@chromium.org>, "Alex Lau" <alexlau@chromium.org>, "Daniel Vetter" <daniel@ffwll.ch>, "Dylan Reid" <dgreid@chromium.org>, "David Staessens" <dstaessens@chromium.org>, "Dmitry Sepp" <dmitry.sepp@opensynergy.com>, "Enrico Granata" <egranata@google.com>, "Frediano Ziglio" <fziglio@redhat.com>, "Hans Verkuil" <hverkuil@xs4all.nl>, "Stéphane Marchesin" <marcheu@chromium.org>, "Pawel Osciak" <posciak@chromium.org>, spice-devel@lists.freedesktop.org, "David Stevens" <stevensd@chromium.org>, "Tomasz Figa" <tfiga@chromium.org>, uril@redhat.com, "Samiullah Khawaja" <samiullah.khawaja@opensynergy.com>, "Kiran Pawar" <kiran.pawar@opensynergy.com> Subject: [virtio-dev] Re: [PATCH v3 1/2] virtio-video: Add virtio video device specification Date: Thu, 27 Feb 2020 16:24:00 +0900 [thread overview] Message-ID: <CAD90VcaTJh5MTRggpOmCK2LAryMHha2+7nPkFVTT8N8S06tf-A@mail.gmail.com> (raw) In-Reply-To: <20200225095956.7rtwugfru4dbjj7q@sirius.home.kraxel.org> Thanks for the review, Gerd. Please see my replies inline below. FYI, I'm implementing virtio-video device for ChromeOS that works with Dmitry's virtio-video driver https://patchwork.linuxtv.org/patch/61717/. Once it becomes fully functional, I'll post a list of possible improvements of protocol. On Tue, Feb 25, 2020 at 7:00 PM Gerd Hoffmann <kraxel@redhat.com> wrote: > > On Thu, Feb 06, 2020 at 07:20:57PM +0900, Keiichi Watanabe wrote: > > From: Dmitry Sepp <dmitry.sepp@opensynergy.com> > > > > The virtio video encoder device and decoder device provide functionalities to > > encode and decode video stream respectively. > > Though video encoder and decoder are provided as different devices, they use a > > same protocol. > > > > Signed-off-by: Dmitry Sepp <dmitry.sepp@opensynergy.com> > > Signed-off-by: Keiichi Watanabe <keiichiw@chromium.org> > > Finally found the time for a closer look. > Pretty good overall, some minor nits below ... > > > +\begin{description} > > +\item[\field{version}] is the protocol version that the device talks. > > + The device MUST set this to 0. > > What is the intended use case for this? > > Given that virtio has feature flags to negotiate support for optional > features and protocol extensions between driver and device, why do you > think this is needed? While feature flags work well when we "extend" the protocol with an optional feature, they don't when we want to "drop" or "modify" features. For example, I guess it'd be useful when we want: * to abandon a non-optional command, * to change a non-optional struct's layout,or * to change the order of commands in which the device expects to be sent. Though it might be possible to handle these changes by feature flags, I suspect the version number allow us to transition protocols more smoothly. WDYT? > > > +The format description \field{virtio_video_format_desc} is defined as > > +follows: > > +\begin{lstlisting} > > +enum virtio_video_format { > > + /* Raw formats */ > > + VIRTIO_VIDEO_FORMAT_RAW_MIN = 1, > > + VIRTIO_VIDEO_FORMAT_ARGB8888 = VIRTIO_VIDEO_FORMAT_RAW_MIN, > > + VIRTIO_VIDEO_FORMAT_BGRA8888, > > + VIRTIO_VIDEO_FORMAT_NV12, /* 12 Y/CbCr 4:2:0 */ > > + VIRTIO_VIDEO_FORMAT_YUV420, /* 12 YUV 4:2:0 */ > > + VIRTIO_VIDEO_FORMAT_YVU420, /* 12 YVU 4:2:0 */ > > + VIRTIO_VIDEO_FORMAT_RAW_MAX = VIRTIO_VIDEO_FORMAT_YVU420, > > I'm wondering what the *_MIN and *_MAX values here (and elsewhere) are > good for? I doubt drivers would actually loop over formats from min to > max, I'd expect they check for specific formats they can handle instead. > > If you want define the range for valid raw formats I'd suggest to leave > some room, so new formats can be added without changing MAX values, i.e. > use -- for example -- RAW_MIN = 0x100, RAW_MAX = 0x1ff, CODED_MIN=0x200, > CODED_MAX=0x2ff. Or just drop them ... Ah, that's a good point. I agree that drivers don't need to loop over formats. If they need, they can define such an alias locally. Still, I guess it's worth defining the range for valid raw/coded formats. This allows devices to report more detailed errors if a driver sent an unexpected format. i.e. "opposite format type" v.s. "unknown format" So, I'd use your idea of RAW_MIN = 0x100 and RAW_MAX = 0x1ff. > > > +struct virtio_video_query_control_level { > > + le32 profile; /* One of VIRTIO_VIDEO_PROFILE_* */ > ^^^^^^^ LEVEL ? Nope, it should be profile. This "profile" field is specified by the driver to query supported levels for a specific profile. In my understanding, supported levels depend on profiles. At least, the specification of H.264 [1] says that `"levels" are specified within each profile.` at section "0.5 Profiles and levels". [1] https://www.itu.int/rec/T-REC-H.264-201906-I/en Best regards, Keiichi > > cheers, > Gerd > --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
next prev parent reply other threads:[~2020-02-27 7:24 UTC|newest] Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-02-06 10:20 [PATCH v3 0/2] Virtio video device specification Keiichi Watanabe 2020-02-06 10:20 ` [virtio-dev] " Keiichi Watanabe 2020-02-06 10:20 ` [PATCH v3 1/2] virtio-video: Add virtio " Keiichi Watanabe 2020-02-06 10:20 ` [virtio-dev] " Keiichi Watanabe 2020-02-25 9:59 ` Gerd Hoffmann 2020-02-25 9:59 ` [virtio-dev] " Gerd Hoffmann 2020-02-27 7:24 ` Keiichi Watanabe [this message] 2020-02-27 7:24 ` Keiichi Watanabe 2020-02-27 9:28 ` Gerd Hoffmann 2020-02-27 9:28 ` [virtio-dev] " Gerd Hoffmann 2020-03-04 4:31 ` Alexandre Courbot 2020-03-04 4:31 ` [virtio-dev] " Alexandre Courbot 2020-03-04 6:42 ` Gerd Hoffmann 2020-03-04 6:42 ` [virtio-dev] " Gerd Hoffmann 2020-03-04 10:07 ` Alexandre Courbot 2020-03-04 10:07 ` [virtio-dev] " Alexandre Courbot 2020-03-23 12:07 ` Keiichi Watanabe 2020-03-23 12:07 ` [virtio-dev] " Keiichi Watanabe 2020-03-23 13:28 ` Dmitry Sepp 2020-03-23 13:28 ` [virtio-dev] " Dmitry Sepp 2020-03-23 15:48 ` Keiichi Watanabe 2020-03-23 15:48 ` [virtio-dev] " Keiichi Watanabe 2020-03-25 9:47 ` Dmitry Sepp 2020-03-25 9:47 ` [virtio-dev] " Dmitry Sepp 2020-03-27 3:35 ` Keiichi Watanabe 2020-03-27 3:35 ` [virtio-dev] " Keiichi Watanabe 2020-03-30 9:53 ` Dmitry Sepp 2020-03-30 9:53 ` [virtio-dev] " Dmitry Sepp 2020-04-06 9:32 ` Alexandre Courbot 2020-04-06 9:32 ` [virtio-dev] " Alexandre Courbot 2020-04-06 11:46 ` Keiichi Watanabe 2020-04-06 11:46 ` [virtio-dev] " Keiichi Watanabe 2020-04-07 9:21 ` Dmitry Sepp 2020-04-07 9:21 ` [virtio-dev] " Dmitry Sepp 2020-04-09 10:46 ` Keiichi Watanabe 2020-04-09 10:46 ` [virtio-dev] " Keiichi Watanabe 2020-04-17 8:08 ` Dmitry Sepp 2020-04-17 8:08 ` [virtio-dev] " Dmitry Sepp 2020-04-20 9:57 ` Keiichi Watanabe 2020-04-20 9:57 ` [virtio-dev] " Keiichi Watanabe 2020-04-21 8:38 ` Dmitry Sepp 2020-04-21 8:38 ` [virtio-dev] " Dmitry Sepp 2020-04-24 11:42 ` Keiichi Watanabe 2020-04-24 11:42 ` [virtio-dev] " Keiichi Watanabe 2020-04-27 14:28 ` Dmitry Sepp 2020-04-27 14:28 ` [virtio-dev] " Dmitry Sepp 2020-04-07 14:49 ` Dmitry Sepp 2020-04-07 14:49 ` [virtio-dev] " Dmitry Sepp 2020-04-09 10:46 ` Keiichi Watanabe 2020-04-09 10:46 ` [virtio-dev] " Keiichi Watanabe 2020-04-09 13:13 ` Dmitry Sepp 2020-04-09 13:13 ` [virtio-dev] " Dmitry Sepp 2020-04-24 11:45 ` Keiichi Watanabe 2020-04-24 11:45 ` [virtio-dev] " Keiichi Watanabe 2020-04-27 9:33 ` Dmitry Sepp 2020-04-27 9:33 ` [virtio-dev] " Dmitry Sepp 2020-05-18 5:17 ` Keiichi Watanabe 2020-05-18 5:17 ` [virtio-dev] " Keiichi Watanabe 2020-05-27 12:12 ` Dmitry Sepp 2020-05-27 12:12 ` [virtio-dev] " Dmitry Sepp 2020-05-29 14:21 ` Keiichi Watanabe 2020-05-29 14:21 ` [virtio-dev] " Keiichi Watanabe 2020-06-01 7:19 ` Alexandre Courbot 2020-06-01 7:19 ` [virtio-dev] " Alexandre Courbot 2020-02-06 10:20 ` [PATCH v3 2/2] virtio-video: Define a feature for exported objects from different virtio devices Keiichi Watanabe 2020-02-06 10:20 ` [virtio-dev] " Keiichi Watanabe 2020-02-25 10:01 ` Gerd Hoffmann 2020-02-25 10:01 ` [virtio-dev] " Gerd Hoffmann 2020-02-27 7:24 ` Keiichi Watanabe 2020-02-27 7:24 ` [virtio-dev] " Keiichi Watanabe
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