linux-kernel - Re: [PATCH v2] soundwire: SDCA: add helper macro to access controls

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Message-ID: <2ab412c5-bf96-5ba3-c193-5a8ad9071bbb@linux.intel.com>
Date:   Mon, 17 Aug 2020 10:14:25 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, gregkh@...uxfoundation.org,
        jank@...ence.com, srinivas.kandagatla@...aro.org,
        rander.wang@...ux.intel.com, ranjani.sridharan@...ux.intel.com,
        hui.wang@...onical.com, sanyog.r.kale@...el.com,
        mengdong.lin@...el.com, bard.liao@...el.com
Subject: Re: [PATCH v2] soundwire: SDCA: add helper macro to access controls

>> The upcoming SDCA (SoundWire Device Class Audio) specification defines
>> a hiearchical encoding to interface with Class-defined capabilities,
> 
> typo hiearchical

ok

>> based on which audio function, entity, control and channel being used.
> 
> Can you please elaborate on what do these terms refer to?
> 
> Also can we have some documentation for this and how Linux is going to
> use it..

These are concepts in the SDCA draft spec, and that should be the 
reference. We worked with MIPI so that this spec will be available with 
a click-through agreement when ratified, for now it's only available to 
contributors per MIPI bylaws.

If you do not have access to this specification, then that's a real 
problem. Maybe you need to let Bard take care of this part as a 
co-maintainer?

The goal with this macro is to enable a first set of codecs drivers 
using these concepts to be released upstream. All you need to know at 
this point is that controls are defined in a hierarchical way and 
accessed with a read/write transaction from/to the address created with 
the following macro.

>> +/* v1.2 device - SDCA address mapping */
>> +#define SDW_SDCA_CTL(fun, ent, ctl, ch)		(BIT(30) |			\
>> +						 (((fun) & 0x7) << 22) |	\
>> +						 (((ent) & 0x40) << 15) |	\
>> +						 (((ent) & 0x3f) << 7) |	\
>> +						 (((ctl) & 0x30) << 15) |	\
>> +						 (((ctl) & 0x0f) << 3) |	\
>> +						 (((ch) & 0x38) << 12) |	\
>> +						 ((ch) & 0x07))
>> +
> 
> how about adding an underscore to the arguments here:
> 
> #define SDW_SDCA_CTL(_fun, _ent, _ctl, _ch)
> and so on..

I checked the SoundWire defines and the vast majority of the macros 
don't use underscores, and when they do there's no consistency between 1 
or 2 underscores.