Re: ASoC: snd_soc_info_volsw and platfrom_max

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On 16/08/2022 14:11, Mark Brown wrote:
On Mon, Aug 15, 2022 at 10:22:37AM +0100, Srinivas Kandagatla wrote:

before this patch the controls max value was calculated considering the min
value, but with this patch this calculation has changed resulting in low
volume on most of the codecs that are using SOC_SINGLE_S8_TLV.

Right, the whole situation is unclear.  At various points the code
hasn't agreed with itself ragarding what the platform_max is relative
to, if it's taken into account and all both within individual control
types and also between control types.

snd_soc_put_volsw does the right thing by considering mc->min, but
info_volsw does it differently.

Below change fixes the issue for me, but I am bit confused with the first
line of this function that calculates max value as max = mc->max - mc->min
and then limits it to platform_max.

The issue is that it's not clear if the platform_max value should be a
value for the register or a value for the control.  For some reason
(which frankly is the source of a lot of the problems here) the controls
adjust the user visible range to be zero based even though the ABI would
be totally fine with any range.  There were out of tree patches that
changed things for some of the control types too.

Only Instances where platform_max is set are via kcontrol builder macros, which then always sets this to xmax.

And none of these macros have provision to pass platform_max these are always assumed to be xmax. Which am not sure is always correct.


diff --git a/sound/soc/soc-ops.c b/sound/soc/soc-ops.c
index bd88de056358..49fb34609202 100644
--- a/sound/soc/soc-ops.c
+++ b/sound/soc/soc-ops.c
@@ -196,7 +196,7 @@ int snd_soc_info_volsw(struct snd_kcontrol *kcontrol,

  	uinfo->count = snd_soc_volsw_is_stereo(mc) ? 2 : 1;
  	uinfo->value.integer.min = 0;
-	uinfo->value.integer.max = max;
+	uinfo->value.integer.max = max  - mc->min;

That'll then break anything that doesn't set platform_max since we'll
apply mc->min twice, you'd need to do the adjustment at the point where
Yes, I agree.

something like this might work.

diff --git a/sound/soc/soc-ops.c b/sound/soc/soc-ops.c
index bd88de056358..cc3b12ace295 100644
--- a/sound/soc/soc-ops.c
+++ b/sound/soc/soc-ops.c
@@ -179,7 +179,7 @@ int snd_soc_info_volsw(struct snd_kcontrol *kcontrol,
 	const char *vol_string = NULL;
 	int max;

-	max = uinfo->value.integer.max = mc->max - mc->min;
+	max = uinfo->value.integer.max = mc->max;
 	if (mc->platform_max && mc->platform_max < max)
 		max = mc->platform_max;

@@ -196,7 +196,7 @@ int snd_soc_info_volsw(struct snd_kcontrol *kcontrol,

 	uinfo->count = snd_soc_volsw_is_stereo(mc) ? 2 : 1;
 	uinfo->value.integer.min = 0;
-	uinfo->value.integer.max = max;
+	uinfo->value.integer.max = max  - mc->min;

 	return 0;
 }

we apply the platform_max override.  Keeping platform_max a register
value is *probably* the least bad thing here.

platform_max being a max register value seems more sensible.

But again if agree on that.

Current state of platform_max which is never set correctly if we use any helper macros is confusing.

Do you think having an explicit macros that take platform_max argument from drivers makes sense?

This will also bring in some clarity.


--srini



  	return 0;
  }


Or should we fix the macro to set platform_max to be max - min.

We shouldn't be changing the static data at all, that's one of the
problems.



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