ASoC: soc-cache: Add support for LZO register caching

This patch adds support for LZO compression when storing the register
cache.  The initial register defaults cache is marked as __devinitconst
and the only change required for a driver to use LZO compression is
to set the compress_type member in codec->driver to SND_SOC_LZO_COMPRESSION.

For a typical device whose register map would normally occupy 25kB or 50kB
by using the LZO compression technique, one can get down to ~5-7kB.  There
might be a performance penalty associated with each individual read/write
due to decompressing/compressing the underlying cache, however that should not
be noticeable.  These memory benefits depend on whether the target architecture
can get rid of the memory occupied by the original register defaults cache
which is marked as __devinitconst.  Nevertheless there will be some memory
gain even if the target architecture can't get rid of the original register
map, this should be around ~30-32kB instead of 50kB.
Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

include/sound/soc.h

@@ -256,7 +256,8 @@ enum snd_soc_control_type {
 };
 
 enum snd_soc_compress_type {
-	SND_SOC_NO_COMPRESSION
+	SND_SOC_NO_COMPRESSION,
+	SND_SOC_LZO_COMPRESSION
 };
 
 int snd_soc_register_platform(struct device *dev,

sound/soc/Kconfig

@@ -4,6 +4,8 @@
 
 menuconfig SND_SOC
 	tristate "ALSA for SoC audio support"
+	select LZO_COMPRESS
+	select LZO_DECOMPRESS
 	select SND_PCM
 	select AC97_BUS if SND_SOC_AC97_BUS
 	select SND_JACK if INPUT=y || INPUT=SND