SPI: add 3wire mode flag

Add a new spi->mode bit: SPI_3WIRE, for chips where the SI and SO signals
are shared (and which are thus only half duplex).  Update the LM70 driver
to require support for that hardware mode from the controller.

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, 4 insertions, 0 deletions

diff --git a/drivers/hwmon/lm70.c b/drivers/hwmon/lm70.c
index 7eaae3834e15..275d392eca61 100644
--- a/drivers/hwmon/lm70.c
+++ b/drivers/hwmon/lm70.c
@@ -96,6 +96,10 @@ static int __devinit lm70_probe(struct spi_device *spi)
         struct lm70 *p_lm70;
         int status;
 
+        /* signaling is SPI_MODE_0 on a 3-wire link (shared SI/SO) */
+        if ((spi->mode & (SPI_CPOL|SPI_CPHA)) || !(spi->mode & SPI_3WIRE))
+                return -EINVAL;
+
         p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
         if (!p_lm70)
                 return -ENOMEM;