[alsa-devel] [PATCH 2/2] snd-usb-audio: Add duplex mode for Digidesign Mbox 1 and enable mixer

[Takashi Iwai]

At Sun, 09 Nov 2014 00:35:29 +1100,
Damien Zammit wrote:
> 
> Hi Takashi,
> 
> On 07/11/14 01:15, Takashi Iwai wrote:
> > Hmm, can we achieve this without introducing the new audioformats
> > thing, e.g. with COMPOSITE, instead?
> 
> I don't think COMPOSITE will work because the same interface has
> multiple endpoints.  My code provides a framework for other devices with
> the same issue.  I was told previously that this was the problem with
> getting my previous attempt into the kernel.  Or is this doable without
> adding a struct?

I think the only point is the check in create_composite_quirk(), where
it marks the iface as claimed and skips the next entry that has been
already claimed.  However, the current code looks inconsistent -- it
allows multiple entries only if the iface matches with the current
one.  Fixing it like below would make things working.

It's a quick idea, so a bit more reviews would be needed, though.
Clemens, what do you think?

BTW, I won't take a look at you v2 series.  If the change above really
works, I'll brush up the patch below properly, so that you can include
in your new patch series.

Last but not least, please add maintainers to Cc when you post patches
for reviewing.


thanks,

Takashi

---
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -58,9 +58,17 @@ static int create_composite_quirk(struct snd_usb_audio *chip,
 		err = snd_usb_create_quirk(chip, iface, driver, quirk);
 		if (err < 0)
 			return err;
-		if (quirk->ifnum != probed_ifnum)
+	}
+
+	for (quirk = quirk->data; quirk->ifnum >= 0; ++quirk) {
+		iface = usb_ifnum_to_if(chip->dev, quirk->ifnum);
+		if (!iface)
+			continue;
+		if (quirk->ifnum != probed_ifnum &&
+		    !usb_interface_claimed(iface))
 			usb_driver_claim_interface(driver, iface, (void *)-1L);
 	}
+
 	return 0;
 }