spi: add ability to validate xfer->bits_per_word in SPI core

Allow SPI masters to define the set of bits_per_word values they support.
If they do this, then the SPI core will reject transfers that attempt to
use an unsupported bits_per_word value. This eliminates the need for each
SPI driver to implement this checking in most cases.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index f996c600eb8c..0cabf1560550 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1377,6 +1377,14 @@ static int __spi_async(struct spi_device *spi, struct spi_message *message)
                         xfer->bits_per_word = spi->bits_per_word;
                 if (!xfer->speed_hz)
                         xfer->speed_hz = spi->max_speed_hz;
+                if (master->bits_per_word_mask) {
+                        /* Only 32 bits fit in the mask */
+                        if (xfer->bits_per_word > 32)
+                                return -EINVAL;
+                        if (!(master->bits_per_word_mask &
+                                        BIT(xfer->bits_per_word - 1)))
+                                return -EINVAL;
+                }
         }
 
         message->spi = spi;