regmap: spi: Handle async writes of only one buffer

If the value is zero then assume it has been included in the register data
and don't send anything, minimising the number of interactions with the
hardware.

Signed-off-by: Mark Brown <broonie@linaro.org>

diff --git a/drivers/base/regmap/regmap-spi.c b/drivers/base/regmap/regmap-spi.c
index 4c506bd940f372b8bbe3b630a9599ca52ea745bf..37f12ae7aadaeadc60005b2bced37ac05bc7210d 100644 (file)
--- a/drivers/base/regmap/regmap-spi.c
+++ b/drivers/base/regmap/regmap-spi.c
@@ -73,7 +73,8 @@ static int regmap_spi_async_write(void *context,
 
        spi_message_init(&async->m);
        spi_message_add_tail(&async->t[0], &async->m);
-       spi_message_add_tail(&async->t[1], &async->m);
+       if (val)
+               spi_message_add_tail(&async->t[1], &async->m);
 
        async->m.complete = regmap_spi_complete;
        async->m.context = async;