On 2016年02月20日 01:11, Takashi Iwai wrote: > On Fri, 19 Feb 2016 17:04:14 +0100, > Takashi Iwai wrote: >> >> On Fri, 19 Feb 2016 16:51:55 +0100, >> Takashi Sakamoto wrote: >>> >>> On Feb 19 2016 18:46, Takashi Iwai wrote: >>>> On Fri, 19 Feb 2016 10:23:36 +0100, >>>> Takashi Sakamoto wrote: >>>>> >>>>> Hi, >>>>> >>>>> On Feb 19 2016 17:19, Takashi Iwai wrote: >>>>>> On Fri, 19 Feb 2016 01:55:50 +0100, >>>>>> Takashi Sakamoto wrote: >>>>>>> >>>>>>> With a previous commit, ALSA oxfw driver retries transferring MIDI >>>>>>> messages at transaction failure for scs1x. On the other hand, there're >>>>>>> fatal transaction error. Then, MIDI messages never reach to the unit >>>>>>> anymore. In this case, MIDI substream should be discontinued. >>>>>>> >>>>>>> This commit stops MIDI transferring after the fatal error occurs. >>>>>>> Unfortunately, unlike ALSA PCM functionality, ALSA rawmidi core has no >>>>>>> feature to discontinue MIDI substream in kernel side, thus this commit >>>>>>> just stops MIDI transferring without notifying it to userspace. >>>>>> >>>>>> It's fine to take this, and I would take it as is for now. >>>>> >>>>> OK. >>>>> >>>>>> But we can extend the rawmidi somehow to deal with such an error, too. >>>>>> Maybe just having "error" flag in the rawmidi runtime and adding a >>>>>> helper function to set the error and stop the stream should work >>>>>> easily. >>>>> >>>>> You forgot ALSA sequencer. >>>> >>>> This is a different layer. The sequencer stuff may check the error >>>> and handle more gracefully than as of now, but it's a different story >>>> from the extension of rawmidi itself. >>>> >>>> What you're working on is the rawmidi, and what it can give is just >>>> returning an error at the right moment. >>> >>> I don't think so. I think the work is heavier than your expectation. >>> >>> I pushed 'rawmidi-epipe' branch to my repository. >>> https://github.com/takaswie/sound/tree/rawmidi-epipe >>> >>> You can see four commits just to show my concerns. >>> (They're not tested yet. Don't use them for actual work ;) >>> 41f499b ALSA: rawmidi: add a helper to set runtime error >>> 4164edb ALSA: rawmidi: handle EPIPE >>> 5e7348ed ALSA: seq: handle EPIPE for rawmidi input >>> 58d9008 ALSA: seq: handle EPIPE for rawmidi output >>> >>> In the top-most commit, you can see userspace applications need to >>> close/open character devices to recover from EPIPE state of rawmidi >>> substream runtime. >> >> Yes, this doesn't change from the current situation. >> >> Remember that rawmidi may return an error already in the current >> implementation. The new feature would be just to add the explicit >> trigger of the error, instead of implicit runtime->avail check. > > BTW, you'd need to put more error checks. There are other loops in > snd_rawmidi_read() and snd_rawmidi_write() before > snd_rawmidi_kernel_read1() and snd_rawmidi_kernel_write1() is reached. > The check is needed there, too. OK, thanks. I'll check it later and it's time to go to bed. zzz Takashi Sakamoto _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
