Laurent Pinchart wrote: > On Monday 13 December 2010 17:10:51 Clemens Ladisch wrote: >> TYPE_EXT describes entities that represent some interface to the >> external world, TYPE_INT those that are internal to the entire device. >> (I'm not sure if that distinction is very useful, but TYPE_SUBDEV seems >> to be an even more meaningless name.) > > SUBDEV comes from the V4L2 world, and I agree that it might not be a very good > name. > > I'm not sure I would split entities in internal/external categories. I would > create a category for connectors though. I'm not disagreeing, but what is actually the distinction between types and subtypes? ;-) >> * Entity properties >> >> There needs to be a mechanism to associate meta-information (properties) >> with entities. This information should be optional and extensible, but, >> when being handled inside the kernel, doesn't need to be more than >> a read-only blob. I think that something like ALSA's TLV format (used >> for mixer controls) can be used here. (I'm not mentioning the X-word >> here, except to note that the "M" stands for "markup".) > > I've been thinking of adding a new ioctl for that. It's something we need to > draft. The UVC driver will need it, and I'm pretty sure other V4L2 drivers > would find it useful as well. I'm imagining a "read-the-properties" ioctl that just returns the entity's blob. >> EXT_SPEAKER also includes headphones; there might be made a case for >> having those as a separate subtype. > > Shouldn't headphones be represented by an EXT_JACK_ANALOG ? Headphone jacks are jacks; there are also USB headphones. >> EXT_BROADCAST represents devices like TV tuners, satellite receivers, >> cable tuners, or radios. > > There's clearly an overlap with V4L here. These come from the USB audio spec. Video devices are indeed likely to be more detailed than just a single audio source. :) >> INT_CONTROLS may have multiple independent controls (this is USB's >> Feature Unit); INT_EFFECT may have multiple controls that affect one >> single algorithm. > > I'd describe this as a feature unit/processing unit then. I was aiming for more descriptive names, but I agree that the original names might be more useful. > Should we have an AUDIO category ? Probably not, because there are combined audio/video jacks, any maybe other entities. >> * Entity specifications >> >> While TYPE_DEVICE entities can be identified by their device node, other >> entities typcially have just a numeric ID. > > In V4L2 sub-devices have (or rather will have once the media controller > patches will be integrated) device nodes as well, so exposing that information > is required. USB and HDA entities already have numeric IDs. >> For that, it would be useful to make do without separate identification and >> let the driver choose the entity ID. > > How would drivers do that ? What if you have two instances of the same chip > (a video sensor, audio mixer, ...) on the same board ? Then those would get different IDs; USB descriptors always describe the entire device. Regards, Clemens -- 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
