[alsa-devel] [PATCH 10/10] ALSA: usb-audio: UAC2: support read-only freq control

Eldad Zack eldad at fogrefinery.com
Tue Apr 2 00:45:33 CEST 2013

Hi Torstein,

On Mon, 1 Apr 2013, Torstein Hegge wrote:

> On Sun, Mar 31, 2013 at 17:52:32 +0200, Eldad Zack wrote:
> > Some clocks might be read-only, e.g., external clocks (see also
> > UAC2
> > 
> > In this case, setting the sample frequency will always fail
> > (even if the rate is equal to the current clock rate),
> > therefore do not write, but read the value and compare to the
> > requested rate.
> > 
> > If it doesn't match, return -ENXIO since the clock is invalid for
> > this configuration.
> I think could be more readable if it was built on top of [1]. Then it
> could check the target rate against the prev_rate reported by the device
> and return before the sample rate set, something like:

Thanks, I think it's a good idea. I'll wait with this patch until you 
get your change to Takashi's tree to save some work for everyone.

> @@ -279,6 +275,20 @@ static int set_sample_rate_v2(struct snd_usb_audio *chip, int iface,
>  		prev_rate = data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);

You might also want to convert this into le32_to_cpu, etc. like in 
patch #5 of this series -- note that as Clemens said, the type should 
should be __le32 (and not u32).


Thanks for pointing out the formatting issues, I'll fix these before 


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