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authorDavid Brownell <dbrownell@users.sourceforge.net>2009-06-30 11:41:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-30 18:56:00 -0700
commitb55f627feeb9d48fdbde3835e18afbc76712e49b (patch)
tree1c6084d44f23c5e70040e5d62c93718f77ad09da /include
parentc49568235dd7b4a2ffad63aa950562f4ffb9455f (diff)
spi: new spi->mode bits
Add two new spi_device.mode bits to accomodate more protocol options, and pass them through to usermode drivers: * SPI_NO_CS ... a second 3-wire variant, where the chipselect line is removed instead of a data line; transfers are still full duplex. This obviously has STRONG protocol implications since the chipselect transitions can't be used to synchronize state transitions with the SPI master. * SPI_READY ... defines open drain signal that's pulled low to pause the clock. This defines a 5-wire variant (normal 4-wire SPI plus READY) and two 4-wire variants (READY plus each of the 3-wire flavors). Such hardware flow control can be a big win. There are ADC converters and flash chips that expose READY signals, but not many host controllers support it today. The spi_bitbang code should be changed to use SPI_NO_CS instead of its current nonportable hack. That's a mode most hardware can easily support (unlike SPI_READY). Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: "Paulraj, Sandeep" <s-paulraj@ti.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/spi/spi.h2
-rw-r--r--include/linux/spi/spidev.h2
2 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 9c4cd27f468..743c933ac4e 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -80,6 +80,8 @@ struct spi_device {
#define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */
#define SPI_3WIRE 0x10 /* SI/SO signals shared */
#define SPI_LOOP 0x20 /* loopback mode */
+#define SPI_NO_CS 0x40 /* 1 dev/bus, no chipselect */
+#define SPI_READY 0x80 /* slave pulls low to pause */
u8 bits_per_word;
int irq;
void *controller_state;
diff --git a/include/linux/spi/spidev.h b/include/linux/spi/spidev.h
index 95251ccd5a0..bf0570a84f7 100644
--- a/include/linux/spi/spidev.h
+++ b/include/linux/spi/spidev.h
@@ -40,6 +40,8 @@
#define SPI_LSB_FIRST 0x08
#define SPI_3WIRE 0x10
#define SPI_LOOP 0x20
+#define SPI_NO_CS 0x40
+#define SPI_READY 0x80
/*---------------------------------------------------------------------------*/