SPI controller drivers: check for unsupported modes

Minor SPI controller driver updates: make the setup() methods reject
spi->mode bits they don't support, by masking aginst the inverse of bits
they *do* support.  This insures against misbehavior later when new mode
bits get added.

Most controllers can't support SPI_LSB_FIRST; more handle SPI_CS_HIGH.
Support for all four SPI clock/transfer modes is routine.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 5 deletions

diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index 88425e1af4d3..0c85c984ccb4 100644
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -187,12 +187,10 @@ int spi_bitbang_setup(struct spi_device *spi)
 
         bitbang = spi_master_get_devdata(spi->master);
 
-        /* REVISIT: some systems will want to support devices using lsb-first
-         * bit encodings on the wire.  In pure software that would be trivial,
-         * just bitbang_txrx_le_cphaX() routines shifting the other way, and
-         * some hardware controllers also have this support.
+        /* Bitbangers can support SPI_CS_HIGH, SPI_3WIRE, and so on;
+         * add those to master->flags, and provide the other support.
          */
-        if ((spi->mode & SPI_LSB_FIRST) != 0)
+        if ((spi->mode & ~(SPI_CPOL|SPI_CPHA|bitbang->flags)) != 0)
                 return -EINVAL;
 
         if (!cs) {