2017-12-19 2:13 GMT+09:00 Takashi Iwai tiwai@suse.de:
On Mon, 18 Dec 2017 18:05:18 +0100, Mauro Santos wrote:
On 18-12-2017 15:45, Takashi Iwai wrote:
On Mon, 18 Dec 2017 16:30:13 +0100, Mauro Santos wrote:
On 18-12-2017 13:53, Takashi Iwai wrote:
On Mon, 18 Dec 2017 14:44:44 +0100, Greg KH wrote:
On Sun, Dec 17, 2017 at 06:56:05PM +0000, Mauro Santos wrote: > I believe this is the right place to report this problem, but if it > isn't please point me in the right direction.
Adding the developer of that patch, and the sound maintainer and developers to the thread.
> I have noticed that after the update from kernel 4.14.5 to 4.14.6 > alsamixer does not show the usual volume controls for my usb soundcard. > > Reverting 3884d12e17ab770aa0f5d4bc65bfbfd006f417fa ALSA: usb-audio: Add > check return value for usb_string() (from linux-stable) makes the > controls come back again with kernel 4.14.6.
(snip)
This is odd, Takashi, I thought we fixed up the problem that if the string was invalid, the code would continue to go on, it's not a "real" error. Did that not get marked for the stable trees?
Yes, it was marked as stable, and it's odd that the revert of the given commit changes the behavior in that way.
Mauro, could you double-check whether reverting the commit really does fix it as expected? If yes, could you put some debug print at the part the patch touches, and check which unit id gives len=0 from snd_usb_copy_string_desc()?
I'm sure reverting that patch makes things work as expected. I noticed the problem after an update and that is the only thing I revert on top of the kernel provided by the distro (Arch Linux).
Did you revert only one patch, not both patches? Just to be sure.
I have reverted only one patch.
Alsamixer works fine for the built in soundcard in my laptop, but the mixer for the usb soundcard was not working so it's specific to usb and only 2 patches touch the mixer.c file between 4.14.5 and 4.14.6. I've tried reversing both, one at a time, and only reverting this one restored the expected behavior.
Regarding adding the debug print I'm going to need guidance. Without reverting anything, would adding at line 2178 of sound/usb/mixer.c the following be enough?
printk("usbmixdbg: nameid=%d len=%d id.name=%s\n",nameid,len,kctl->id.name);
It would then look like this (minus the line wrapping): len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name)); printk("usbmixdbg: nameid=%d len=%d id.name=%s\n",nameid,len,kctl->id.name); if (len)
Well, at that point, there should be no difference. The difference is after that, so what I'd like to see is something like:
--- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2175,14 +2175,18 @@ static int parse_audio_selector_unit(struct mixer_build *state, int unitid,
nameid = uac_selector_unit_iSelector(desc); len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
- pr_info("XXX id=%d, check_mapped_name=%d\n", id, len); if (len) ;
- else if (nameid)
- else if (nameid) { len = snd_usb_copy_string_desc(state, nameid, kctl->id.name, sizeof(kctl->id.name));
- else
pr_info("XXX id=%d, copy_string=%d\n", len);} else { len = get_term_name(state, &state->oterm, kctl->id.name, sizeof(kctl->id.name), 0);
pr_info("XXX id=%d, get_term_name=%d\n", len);}
if (!len) { strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));
If you see copy_string=0, it means that your hardware reports a bogus entry, and the driver does it correctly. If ignoring that error really restores the old behavior back, it essentially means that it worked casually in the past...
I have applied your patch on top of 4.14.7 without reverting anything and I was planning to reply only after I had some result but building failed (without any errors strangely).
I took a second look at your patch and I have a (maybe silly/naive) question, don't the second and third pr_info calls need an extra argument? There are two %d in the string but only one variable (len).
Yeah, sure, of course you need them :) I haven't tested the patch, but just to give you an idea. Sorry if you wasted your time due to that.
OK. I will make a debug patch with you last debug code.
--- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -656,10 +656,14 @@ static int get_term_name(struct mixer_build *state, struct usb_audio_term *iterm unsigned char *name, int maxlen, int term_only) { struct iterm_name_combo *names; + int len;
- if (iterm->name) - return snd_usb_copy_string_desc(state, iterm->name, + if (iterm->name) { + len = snd_usb_copy_string_desc(state, iterm->name, name, maxlen); + if (len) + return len; + }
I will come back soon.
Takashi