At Tue, 15 Nov 2011 14:55:33 +0530, Vinod Koul wrote:
On Tue, 2011-11-15 at 09:11 +0100, Takashi Iwai wrote:
For compressed path (i had posted RFC roughly two months back [1]),
we
are creating new devices /dev/snd/comprCxDxp which would be
registered
as SNDRV_DEV_COMPRESS. For the registration part we need to assign
the
minors, right? Hence the above question
Or did I miss something very obvious here...
Yes, take a look at PCM devices, for example. They have sub-streams. So, you can open a single device file multiple times to assign multiple sub-streams. If any specific substream with a given index is needed, it can be specified via ioctl before open. Otherwise, the next empty substream is assigned.
The similar implementation is found in rawmidi, too.
Okay Thanks a bunch, I wanted to avoid these kind of mistakes :)
right now we don't have PCM devices or substreams notion. The DSP driver registers the compressed_ops (not pcm) with framework and we create the device nodes. framework would call them based on state and file_ops called.
From what I read in rawmidi and your suggestion about PCM devices, I
think you are suggesting to use a single file ops only (this a single minor number (or two, including capture) would suffice instead of a range, right? Any suggestion of which number to use? (well i followed the usually convention of PCM for minor numbers, although I cannot envision a device with multiple/large DSPs for audio offload)
OK, if there aren't so many devices, we may still reserved slots (minor 2 and 3). These can be assigned for the new type. Will be there two completely different DSPs? If it's unlikely, just grab one minor as the start, I'd say. You can still implement the substreams in a single device.
Note that the above story is only for the case without CONFIG_SND_DYNAMIC_MIONRS. If you use CONFIG_SND_DYNAMIC_MINORS (this is usually set for all modern distros), there is no restriction but the total number of minors since the minor numbers are assigned dynamically. So you can forget all in the above.
Takashi