[alsa-devel] [PATCH 01/11] ASoC: rt5651: Avoid duplicating DMI quirks between codec and machine driver

[Hans de Goede]

Hi Mark,

On 21-02-18 20:23, Hans de Goede wrote:
> Hi,
> 
> On 21-02-18 12:54, Mark Brown wrote:
>> On Tue, Feb 20, 2018 at 11:15:01PM +0100, Hans de Goede wrote:
>>> Instead of duplicating the DMI quirks between the codec and machine driver,
>>> add a rt5651_set_pdata() codec private function which the machine driver
>>> can use to pass in pdata.
>>
>> It's not clear to me that this is a great idea.  The goal in general is
>> to keep as much of the CODEC configuration in the CODEC driver as
>> possible so we can move more towards generic machine drivers, this is
>> moving us in the opposite drection quite dramatically.
> 
> Not really, instead of having Intel/ACPI specific quirks in the codec
> driver it moves everything over to pdata, so in a way this unifies the
> device-tree and ACPI paths.
> 
> Also to me it seems that the Intel specific machine driver is the
> logical place to put quirks for Intel platforms rather then poluting the
> platform-agnostic codec driver with this.
> 
>> That might get
>> in the way of improvements we could be making when we get the component
>> based changes further on and can avoid having all the DPCM stuff in the
>> Intel drivers.
>>
>> It is really unfortunate that ACPI based systems aren't embracing
>> standards here and using this mess of open coded quirks but it feels
>> like the way to do this is to keep the code as close as possible to well
>> designed firmware interfaces and hope that they come round.
> 
> Both devicetree and ACPI code-paths are filling pdata and that is the
> only thing the codec driver cares about after this patch. so this is
> using a well designed interface (but a non firmware one). I can understand
> if you would prefer to use the functions from include/linux/property.h
> for this, but those simply do not work for ACPI platforms atm.
> 
> If you look further in this series then quirks for at least 2 more models
> are added and I expect more to show up in the future, I really do not want
> to duplicate these over 2 files.
> 
> One possible solution here would be to add device-properties to the codec
> i2c-device from the machine-driver using device_add_properties() and make
> the codec driver consume those.
> 
> This has probe-ordering issues, but those can be worked around by exporting
> something like the rt5651_apply_pdata() function from this patch and make
> the machine driver call that after it has attached the properties.
> 
> I'm not sure if this extra level of indirection buys us much though, the
> DT binding maintainers will not accept binding docs for these kind of
> kernel internal only device-properties until there are actual DT users
> of them, so for now this would mainly add a bunch of extra code for
> little gain.

So thinking more about this I think that having the codec driver only
check device-properties and completely killing platform_data is the best
way forward / best way to clean this up.

Combined with either device-tree or the machine driver setting these device
properties for now, and in the future the ACPI tables can set these properties
directly and we can hopefully won't need to add new quirks to the machine
driver.

I plan to start reworking this series this afternoon, so any feedback
on the device-properties plan would be appreciated...

Regards,

Hans