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.
Takashi