[alsa-devel] [Device-drivers-devel] [uclinux-dist-devel] [PATCH 1/4] Blackfin: Use 8bit spi transfers for the ad1836

Mike Frysinger vapier at gentoo.org
Fri May 6 15:12:34 CEST 2011

On Fri, May 6, 2011 at 08:48, Mark Brown wrote:
> On Fri, May 06, 2011 at 02:28:32PM +0200, Lars-Peter Clausen wrote:
>> The snd_soc_cache infrastructure has several helper functions for writing spi
>> on a spi bus. The one used by the ad1836 was specifically added for the ad1836
>> and is special compared to the other spi helper functions in the regard that it
>> swaps the upper and the lower byte of the to be transferred data.
>> While this works on blackfin which is litte-endian this scheme will obviously
>> fail on big-endian machines. Also this might not work for other codecs which
>> want to reuse the same helper function.
> So clearly the cache stuff ought to be using cpu_to_be16 for this stuff.
> At present we've been lazy about this as on most CPUs the swap boils
> down to a noop.  If we do end up needing both swaps then we just add
> this as another parameter in the cache infrastructure.

indeed ... this is the direction i'd rather head rather than drop all
the existing stuff down to 8bit only.

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