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>
diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index 88425e1..0c85c98 100644
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -187,12 +187,10 @@
 
 	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) {