diff options
| author |   Michael Buesch <mb@bu3sch.de> | 2009-04-02 16:57:07 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-02 19:04:51 -0700 |
| commit | bfb9bcdbda9a61bca469bf899a589918c60c4c18 (patch) | |
| tree | 40b28178c9d969c94e2039b27ac213cab5de0e79 /include | |
| parent | gpio: gpio_{request,free}() now required (feature removal) (diff) | |
| download | linux-dev-bfb9bcdbda9a61bca469bf899a589918c60c4c18.tar.xz linux-dev-bfb9bcdbda9a61bca469bf899a589918c60c4c18.zip | |
spi-gpio: allow operation without CS signal
Change spi-gpio so that it is possible to drive SPI communications over
GPIO without the need for a chipselect signal.
This is useful in very small setups where there's only one slave device
on the bus.
This patch does not affect existing setups.
I use this for a tiny communication channel between an embedded device and
a microcontroller. There are not enough GPIOs available for chipselect
and it's not needed anyway in this case.
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Cc: David Brownell <david-b@pacbell.net>
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_gpio.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/spi/spi_gpio.h b/include/linux/spi/spi_gpio.h index 0f01a0f1f40c..ca6782ee4b9f 100644 --- a/include/linux/spi/spi_gpio.h +++ b/include/linux/spi/spi_gpio.h @@ -25,10 +25,16 @@ * ... * }; * + * If chipselect is not used (there's only one device on the bus), assign + * SPI_GPIO_NO_CHIPSELECT to the controller_data: + * .controller_data = (void *) SPI_GPIO_NO_CHIPSELECT; + * * If the bitbanged bus is later switched to a "native" controller, * that platform_device and controller_data should be removed. */ +#define SPI_GPIO_NO_CHIPSELECT ((unsigned long)-1l) + /** * struct spi_gpio_platform_data - parameter for bitbanged SPI master * @sck: number of the GPIO used for clock output |