The first patch implements McBSP sidetone feature on OMAP3 while the second one provides ALSA interface for using it.
The patch set is based on the patch Eduardo Valentin sent to alsa-devel mailing list in October 2009. Channel gain control and enabling the sidetone have been moved to ALSA interface as suggested in comments.
Since previous review round, I have corrected both the pointed issues in ASoC patch. In addition, I rebased this patch on top of Janusz Krzysztofik's McBSP register cache patches in linux-omap-2.6.git
Eero Nurkkala (1): McBSP: OMAP3: Add sidetone feature
Ilkka Koskinen (1): ASoC: OMAP-McBSP: ASoC interface for McBSP sidetone
arch/arm/mach-omap2/mcbsp.c | 2 + arch/arm/plat-omap/include/plat/mcbsp.h | 63 +++++ arch/arm/plat-omap/mcbsp.c | 394 ++++++++++++++++++++++++++++++- sound/soc/omap/omap-mcbsp.c | 176 ++++++++++++++ sound/soc/omap/omap-mcbsp.h | 2 + 5 files changed, 636 insertions(+), 1 deletions(-)