[PATCH] ASoC: ops: Shift tested values in snd_soc_put_volsw() by +min

[Marek Vasut]

On 2/23/22 17:32, Mark Brown wrote:
> On Wed, Feb 23, 2022 at 03:55:54PM +0100, Takashi Iwai wrote:
>>
>> But, more reading the code, I suspect whether the function does work
>> correctly at all...  How is the mask calculation done in that way?
>>    unsigned int mask = (1U << (fls(min + max) - 1)) - 1;
>> What's the difference of this function with snd_soc_put_volsw()?
> 
> Yeah, I'm not clear either - Marek mentioned _SX when he was doing the
> patch but I didn't get the bandwidth to figure out what it's doing
> properly yet.  At this point I'm not clear what _SX is supposed to do,
> I'm hoping it works well for the devices that use it but I don't have
> any of them.

Right, I wasn't sure about the remaining two -- volsw_sx and xr_sx -- 
that's why I only did this one I could at least test.

But CS42L51 is on STM32MP1 DKx devkit, CCing Alex , ST might be able to 
look at that one and test.

>> Furthermore, the mask calculation and usage in snd_soc_put_volsw()
>> isn't right, either, I'm afraid; if the range is [-10, 0], max=0, then
>> mask will 0, which will omit all values...
> 
> Indeed, if anyone did that.  Fortunately I don't *think* that's an
> issue.  The whole way that code handles signed bitfields by remapping
> them into unsigned user visible controls is a landmine, it's not even
> obvious that they handle signed bitfields in the first place.

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