On Wed, Mar 05, 2025 at 02:03:58PM +0100, Hans de Goede wrote: > On 3-Mar-25 5:22 PM, Ricardo Ribalda wrote: > > On Mon, 3 Mar 2025 at 17:11, Laurent Pinchart wrote: > >> On Mon, Mar 03, 2025 at 04:43:50PM +0100, Hans de Goede wrote: > >>> On 3-Mar-25 16:13, Laurent Pinchart wrote: > >>>> On Mon, Mar 03, 2025 at 03:47:51PM +0100, Hans de Goede wrote: > >>>>> On 26-Feb-25 14:00, Ricardo Ribalda wrote: > >>>>>> The UVC driver provides two metadata types V4L2_META_FMT_UVC, and > >>>>>> V4L2_META_FMT_D4XX. The only difference between the two of them is that > >>>>>> V4L2_META_FMT_UVC only copies PTS, SCR, size and flags, and > >>>>>> V4L2_META_FMT_D4XX copies the whole metadata section. > >>>>>> > >>>>>> Now we only enable V4L2_META_FMT_D4XX for the Intel D4xx family of > >>>>>> devices, but it is useful for any device where vendors include other > >>>>>> metadata, such as the one described by Microsoft: > >>>>>> - https://learn.microsoft.com/en-us/windows-hardware/drivers/stream/mf-capture-metadata > >>>>>> > >>>>>> This patch removes the UVC_INFO_META macro and enables > >>>>>> V4L2_META_FMT_D4XX for every device. It also updates the documentation > >>>>>> to reflect the change. > >>>>>> > >>>>>> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx> > >>>>> > >>>>> Thanks, patch looks good to me: > >>>>> > >>>>> Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx> > >>>> > >>>> I don't quite agree, sorry. > >>>> > >>>> The reason why the current mechanism has been implemented this way is to > >>>> ensure we have documentation for the metadata format of devices that > >>>> expose metadata to userspace. > >>>> > >>>> If you want to expose the MS metadata, you can create a new metadata > >>>> format for that, and enable it on devices that implement it. > >>> > >>> Looking at the long list of quirks this removes just for the D4xx > >>> cameras I do not believe that having quirked based relaying of > >>> which metadata fmt is used to userspace is something which scales > >>> on the long term. Given the large amount of different UVC cameras > >>> I really think we should move the USB VID:PID -> metadata format > >>> mapping out of the kernel. > >> > >> If we can find a solution to ensure the metadata format gets documented, > >> sure. > > > > MS default metadata is already documented: > > https://learn.microsoft.com/en-us/windows-hardware/drivers/stream/mf-capture-metadata > > > > I would not worry too much about vendors abusing the metadata for > > custom magic if that is your concern. > > This would not work with Windows default driver, and that is what most > > camera modules are tested against. > > > >> When it comes to the MS metadata format, if I recall correctly, Ricardo > >> said there's an XU with a known GUID to detect the metadata format. We > >> therefore wouldn't need quirks. > > > > There is MXSU control > > https://learn.microsoft.com/en-us/windows-hardware/drivers/stream/uvc-extensions-1-5 > > But not all the vendors use it. > > Right so I actually already checked: > > https://learn.microsoft.com/en-us/windows-hardware/drivers/stream/uvc-extensions-1-5 > > yesterday before my udev hwdb suggestion I was wondering if there was a way > to just get if MSmetadata was used from the camera itself. What I found was this: > > "UVC metadata is opt-in. Every IHV/OEM that needs metadata support must be enabled through a custom INF file." > > which lead me to the udev + hwdb suggestion. > > It is good to know that some cameras have a a way to fet this from a known XU GUID, > but the official way seems to be to have per camera info in .inf files. So for Linux > that would translate to having a list of vid:pid combinations somewhere. > > The question then becomes where do we put the vid:pid list and IMHO hwdb is much > better (easier to maintain / update) then hardcoding this in the kernel. Additional questions: where do we store documentation for the metadata format, how do we convey what format is supported to applications, and how do we enable metadata capture when a device is listed in the DB ? -- Regards, Laurent Pinchart
