Hi, Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx> writes: >> Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx> writes: >>> I came to this patch series when wanted to do two things: >>> - use UAC1 as virtual ALSA sound card on gadget side, >>> just like UAC2 is used so it's possible to do rate >>> resampling >>> - have both playback/capture support in UAC1 >>> >>> Since I wanted to have same behavior for both UAC1/UAC2, >>> obviously I've got an utility part (u_audio.c) for >>> virtual ALSA sound card handling like we have >>> for ethernet(u_ether) or serial(u_serial) functions. >>> Function-specific parts (f_uac1/f_uac2) became almost >>> as storage for class-specific USB descriptors, some >>> boilerplate for configfs, binding and few USB >>> config request handling. >>> >>> Originally in RFC [1] I've posted before, there was >>> major change to f_uac1 after that it couldn't do >>> direct play to existing ALSA sound card anymore, >>> representing audio on gadget side as virtual >>> ALSA sound card where audio streams are simply >>> sinked to and sourced from it, so it may break >>> current usecase for some people (and that's why >>> it was RFC). >>> >>> During RFC discussion, it was agreed to not touch >>> existing f_uac1 implementation and create new one >>> instead. This patchset (v4) introduced new function >>> named f_uac1_acard and doesn't touch current f_uac1 >>> implementation, so people still can use old behavior >> >> Do you have a pointer to the original RFC discussion where this was >> discussed? If we really *must* keep the old implementation, I would >> rather rename that to f_uac1_legacy. Still, I find it unlikely that >> anybody will care about the old implementation. > > It is on LKML (which is down for me) [1] or alternative archive [2] > >> >>> Now, it's possible to use existing user-space >>> applications for audio routing between Audio Gadget >>> and real sound card. I personally use alsaloop tool >>> from alsautils and have ability to create PCM >>> loopback between two different ALSA cards using >>> rate resampling, which was not possible with previous >>> "direct play to ALSA card" approach in f_uac1. >> >> this is really good result and will actually make it a lot easier for >> testing things out. >> >>> While here, also dropped redundant platform >>> driver/device creation in f_uac2 driver (as well as >>> didn't add "never implemented" volume/mute functionality >>> in f_uac1 to f_uac1_acard) that made this work even >>> easier to do. >>> >>> This series is tested with both legacy g_audio.ko and >>> modern configfs approaches under Ubuntu 14.04 (UAC1 and >>> UAC2) and under Windows7 x64 (UAC1 only) having >>> perfect results in all cases. >>> >>> Comments, testing are welcome. >>> >>> v4 changes: >>> - renamed f_uac1_newapi to f_uac1_acard that is >>> more meaningful >> >> I really don't get why you wanna keep both f_uac1 and f_uac1_acard. Why >> do we need to maintain the old uac1 implementation? Why two separate >> files? > > In first RFC ([1],[2]) I did exactly what you wrote here (removed > old uac1 implementation and replaced it by new one) but got feedback > that it will break things for existing f_uac1 legacy users and it's better to > have separate implementation. > > I'm OK with dropping legacy f_uac1 implementation. > > Another idea I was thinking about is to implement simple in-kernel > driver which will do the same as existing alsaloop tool userspace > tool does (so legacy users will need to load two kernel modules > and get same functionality). But this seems to be a wrong way, > since It known that Linux kernel community doesn't like to take drivers > with same functionality as existing userspace tools already have. > > So bottom line: since I'm not a legacy f_uac1 user, there is no > difference for me how to handle it - remove legacy f_uac1 completely, > rename it to f_uac1_legacy or add separate f_uac1_acard function. > > So if dropping of legacy f_uac1 implementation is OK for you, > I can do it quickly in next patchset. Personally, I don't want duplicated functionality and I think the virtual sound card approach is much better. Then again, removing functionality we already support is kind of odd. Greg, Alan, what do you guys think? Do we keep a duplicated function around or do we just tell people to rely on alsaloop? Personally, I think we're better off with the flexibility of the virtual sound card, what's your take? -- balbi
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