Re: [PATCH 2/8] ASoC: tegra: Fix AMX byte map

[Sameer Pujar]

On 23-06-2023 15:45, Mark Brown wrote:
> On Fri, Jun 23, 2023 at 11:09:32AM +0530, Sameer Pujar wrote:
> > On 22-06-2023 17:37, Mark Brown wrote:
> > > On Thu, Jun 22, 2023 at 05:04:10PM +0530, Sameer Pujar wrote:
> > > > Byte mask for channel-1 of stream-1 is not getting enabled and this
> > > > causes failures during AMX use cases. The enable bit is not set during
> > > > put() callback of byte map mixer control.
> > > > This happens because the byte map value 0 matches the initial state
> > > > of byte map array and put() callback returns without doing anything.
> > > > Fix the put() callback by actually looking at the byte mask array
> > > > to identify if any change is needed and update the fields accordingly.
> > > I'm not quite sure I follow the logic here - I'd have expected this to
> > > mean that there's a bootstrapping issue and that we should be doing some
> > > more initialisation during startup such that the existing code which
> > > checks if there is a change will be doing the right thing?
> > The issue can happen in subsequent cycles as well if once the user disables
> > the byte map by putting 256. It happens because of following reason where
> > 256 value is reset to 0 since the byte map array is tightly packed and it
> > can't store 256 value.
> ...
>
> > > > Also update get() callback to return 256 if the byte map is disabled.
> > > This will be a user visible change.  It's not clear to me why it's
> > > needed - it seems like it's a hack to push users to do an update in the
> > > case where they want to use channel 1 stream 1?
> > Though it looks like 256 value is forced, but actually the user sees
> > whatever value is set before. The 256 value storage is linked to byte mask
> > value.
> > I must admit that this is not easily readable. If you suggest to simplify
> > this, I can check if storage space increase for byte map value can make it
> > more readable. Thanks for your feedback.
> This could definitely use more clarification I think.  It's not obvious
> that storing 256 won't actually hold (and that should trigger a
> complaint from mixer-test if that's what happens).

OK. I will provide more clarifications in the commit message and the 
driver for the existing failure. Will put a TODO item in the driver to 
improve the logic and make it more readable.