[alsa-devel] [Uclinux-dist-devel] [PATCH 2/2] ASoC: Blackfin AD1836/AD1938 machine drivers: require SPI master

Mike Frysinger vapier.adi at gmail.com
Fri Oct 9 02:01:05 CEST 2009

On Thu, Oct 8, 2009 at 06:01, Mark Brown wrote:
> On Wed, Oct 07, 2009 at 08:27:56PM -0400, Mike Frysinger wrote:
>> i dont think the soc-cache could be used currently by the ad1836 as it
>> doesnt use a 7/9 split with the address/data.  it uses like 6/10 (4
>> addr bits, one bit for read/write, one bit is always 0, and 10 data
>> bits).  guessing the write bit can be considered part of the addr as
>> the read always comes from the cache, but that still gives us 5/10
>> split.  maybe a new 6/10 set of funcs should be added ...
> That's the idea - add new functions for any new register formats.

i'll add a tracker item to get the ad codecs converted to soc-cache
when possible and that'll naturally address the SPI dependency

>> snd_soc_7_9_write() looks like it does a little more bit work than it
>> needs to ?  if data is declared as a u16, then you have:
>> u16 data = (reg << 9) | (value & 0x01ff);
>> this is what the ad1836 driver does now for its data split.
> Probably.  I'd need to check but I believe that's there to handle
> endianness variations in the host, though a cpu_to_ in what you have
> above ought to be able to take care of that.  The code was cut'n'pasted
> from what was in the drivers already.

true ... being little endian sometimes makes you forget about these
things ;).  the ad1836 codec probably doesnt work on BE systems.

>> in the mean time, rather than adding #ifdef to the codec driver, we
>> could create a local header like "bus-stubs.h" that stubs all the
>> relevant functions to an error value.  then all codec drivers that
>> dont use soc-cache can use that instead and the only change needed is
>> to add:
>> #include "bus-stubs.h"
> I'm not sure I feel up to doing that locally in ASoC rather than in the
> relevant subsystems.

i dont feel like convincing subsystem maintainers that this is a good
idea for all consumers of SPI/I2C, especially since i'm not convinced
myself.  we'll just go the soc-cache route and not worry about it.

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