spi-gpio: Support busses without chipselect (only one device on the bus)

SVN-Revision: 14476

target/linux/generic-2.6/patches-2.6.28/920-02-spi-gpio-without-cs.patch

@@ -0,0 +1,77 @@
+Optionally omit the CS signal, if there's only one device on the bus.
+
+--mb
+
+
+
+Index: linux-2.6.28.2/drivers/spi/spi_gpio.c
+===================================================================
+--- linux-2.6.28.2.orig/drivers/spi/spi_gpio.c	2009-02-11 18:48:23.000000000 +0100
++++ linux-2.6.28.2/drivers/spi/spi_gpio.c	2009-02-11 18:48:50.000000000 +0100
+@@ -178,8 +178,10 @@ static void spi_gpio_chipselect(struct s
+ 	if (is_active)
+ 		setsck(spi, spi->mode & SPI_CPOL);
+ 
+-	/* SPI is normally active-low */
+-	gpio_set_value(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
++	if (cs != SPI_GPIO_NO_CHIPSELECT) {
++		/* SPI is normally active-low */
++		gpio_set_value(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
++	}
+ }
+ 
+ static int spi_gpio_setup(struct spi_device *spi)
+@@ -191,15 +193,17 @@ static int spi_gpio_setup(struct spi_dev
+ 		return -EINVAL;
+ 
+ 	if (!spi->controller_state) {
+-		status = gpio_request(cs, spi->dev.bus_id);
+-		if (status)
+-			return status;
+-		status = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
++		if (cs != SPI_GPIO_NO_CHIPSELECT) {
++			status = gpio_request(cs, spi->dev.bus_id);
++			if (status)
++				return status;
++			status = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
++		}
+ 	}
+ 	if (!status)
+ 		status = spi_bitbang_setup(spi);
+ 	if (status) {
+-		if (!spi->controller_state)
++		if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT)
+ 			gpio_free(cs);
+ 	}
+ 	return status;
+@@ -209,7 +213,8 @@ static void spi_gpio_cleanup(struct spi_
+ {
+ 	unsigned long	cs = (unsigned long) spi->controller_data;
+ 
+-	gpio_free(cs);
++	if (cs != SPI_GPIO_NO_CHIPSELECT)
++		gpio_free(cs);
+ 	spi_bitbang_cleanup(spi);
+ }
+ 
+Index: linux-2.6.28.2/include/linux/spi/spi_gpio.h
+===================================================================
+--- linux-2.6.28.2.orig/include/linux/spi/spi_gpio.h	2009-02-11 18:48:23.000000000 +0100
++++ linux-2.6.28.2/include/linux/spi/spi_gpio.h	2009-02-11 18:58:31.000000000 +0100
+@@ -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