Hi Hans, On Monday 02 August 2010 23:01:55 Hans Verkuil wrote: > On Monday 02 August 2010 16:35:54 Laurent Pinchart wrote: > > On Sunday 01 August 2010 13:58:20 Hans Verkuil wrote: > > > On Thursday 29 July 2010 18:06:39 Laurent Pinchart wrote: > > [snip] > > > > > For subdevs you want to return a chip ident and revision field (same as > > > VIDIOC_DBG_G_CHIP_IDENT does). > > > > Do we still need a chip ID when we now have a name ? Keeping the chip ID > > registry updated is painful, it would be nice if we could do away with > > it. > > It's not that easy I think. The name of the subdev entity is set by the > host (bridge) driver Is it ? It should be set by the subdev driver. > and that doesn't know the exact chip ID. E.g. the audio msp3400 subdev > driver actually supports dozens of msp variants. Knowing which variant it is > may actually be important information on an embedded system. > > Note also that the chip ID is optional: it is only required when using the > debug ioctls to get/set registers and to obtain the chip ident. > > > A revision field is a very good idea, I'll add it. > > > > > Should we allow (possibly optional) names for pads? Or 'tooltip'-type > > > descriptions that can be a lot longer than 32 chars? (Just > > > brainstorming here). > > > > > > I am of course thinking of apps where the user can setup the media flow > > > using a GUI. If the driver can provide more extensive descriptions of > > > the various entities/pads, then that would make it much easier for the > > > user to experiment. > > > > It would be nice to have, yes. Some kind of pad capabilities would be > > interesting too. > > What sort of caps do you have in mind? I'm not sure yet. Maybe the kind of media streams the pad supports, things like that. > > > Note that I also think that obtaining such detailed information might > > > be better done through separate ioctls (e.g. MEDIA_IOC_G_PAD_INFO, > > > etc.). > > > > I agree. So we can leave the additional pad information out for now and > > add it later if needed :-) > > > > > What is definitely missing and *must* be added is a QUERYCAP type ioctl > > > that provides driver/versioning info. > > > > I'll create one. > > > > > Another thing that we need to figure out is how to tell the application > > > which audio and video nodes belong together. > > > > What about adding a group ID field in media_entity ? > > It's a possibility, but it's always a bit of a hassle in an application to > work with group IDs. I wonder if there is a more elegant method. The problem is a bit broader than just showing relationships between video nodes and ALSA devices. We also need to show relationships between lens/flash controllers and sensors for instance. Group IDs sound easy, but I'm open to suggestions. > > > Not only that, but we need to be able to inform the driver how audio is > > > hooked up: through an audio loopback cable, an alsa device, > > > > Doesn't the loopback cable connect the audio signal to audio hardware > > that exposes an ALSA device ? How will drivers be able to tell if the > > user has connected a loopback cable and what he has connected it to ? > > If the audio is passed out from the card through a loopback cable, then the > application knows that it has to ask the user for the alsa device. It is > obviously impossible to know in advance which alsa device the card is > hooked up to. > > > > part of an mpeg stream, > > > > In that case there will be no audio device. > > > > > or as a V4L2 audio device (ivtv can do that, and I think pvrusb2 does > > > the same for radio). I'm not entirely sure we want to expose that last > > > option as it is not really spec compliant. > > > > I'm not sure either :-) Why doesn't ivtv use an ALSA device ? > > With earlier firmwares the audio was out of sync with the video so you > needed timestamps to sync them up. And alsa didn't (and doesn't) support > this. Still not ? :-S > > > Other things we may want to expose: is the video stream raw or > > > compressed? > > > > I think that belongs to V4L2. > > V4L2 has something along these lines: VIDIOC_ENUM_FMT can set a COMPRESSED > flag when enumerating formats. After thinking about this a bit more I've > come to the conclusion that for now at least we should keep this in V4L2. OK. > > > What are the default video/audio/vbi streams? (That allows an app to > > > find the default video device node if a driver has lots of them). > > > > What about adding a __u32 flags field to media_entity, and defining a > > MEDIA_ENTITY_FLAG_DEFAULT bit ? > > I had the same idea. Not just useful for alsa, v4l and dvb nodes, but also > for IR inputs. We should look at IR as well: it is nice if you can easily > discover the IR input associated with the board. So a default flag sounds good. > > > Some of this information should perhaps be exposed through the v4l2 > > > API, but other parts definitely belong here. > > > > > > I've not thought about this in detail, but we need to set some time > > > aside to brainstorm on how to provide this information in a logical > > > and consistent manner. > > > > IRC ? A real meeting would be better, but the next scheduled one is in > > November and that's a bit too far away. > > If there is enough to discuss, then an interim meeting might well be > useful. Anther crazy idea: reporting physical location information for subdevs, such as "this sensor is located on the back of the case" or "this sensor faces the user". Some brainstorming is indeed needed. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
