Re: [RFCv2] Add a library to retrieve associated media devices - was: Re: [ANNOUNCE] experimental alsa stream support at xawtv3

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 05/29/2011 01:19 PM, Hans Verkuil wrote:
> Hi Mauro,
>
> Thanks for the RFC! Some initial comments below. I'll hope to do some more
> testing and reviewing in the coming week.
>

<Snip>

>> c) get_not_associated_device: Returns the next device not associated with
>> 			      an specific device type.
>>
>> char *get_not_associated_device(void *opaque,
>> 			    char *last_seek,
>> 			    enum device_type desired_type,
>> 			    enum device_type not_desired_type);
>>
>> The parameters are:
>>
>> opaque:			media devices opaque descriptor
>> last_seek:		last seek result. Use NULL to get the first result
>> desired_type:		type of the desired device
>> not_desired_type:	type of the seek device
>>
>> This function seeks inside the media_devices struct for the next physical
>> device that doesn't support a non_desired type.
>> This method is useful for example to return the audio devices that are
>> provided by the motherboard.
>
> Hmmm. What you really want IMHO is to iterate over 'media hardware', and for
> each piece of hardware you can find the associated device nodes.
>
> It's what you expect to see in an application: a list of USB/PCI/Platform
> devices to choose from.

This is exactly what I was thinking, I was think along the lines of making
the device_type enum bitmasks instead, and have a list devices functions,
which lists all the "physical" media devices as "describing string",
capabilities pairs, where capabilities would include things like sound
in / sound out, etc.

And then a function to get a device string (be it a device node
or an alsa device string, whatever is appropriate) for each capability
of a device.

This does need some more thought for more complex devices though ...

Regards,

Hans