linux-kernel - [PATCH v2 6/6] of_spi: Initialize cs_gpios and cs

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Date:	Tue, 29 Jan 2013 15:53:43 +0100
From:	Andreas Larsson <andreas@...sler.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	Rob Herring <rob.herring@...xeda.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	devicetree-discuss@...ts.ozlabs.org,
	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, software@...sler.com
Subject: [PATCH v2 6/6] of_spi: Initialize cs_gpios and cs_gpio with -EEXIST

Holes in the cs-gpios DT phandle list is supposed to mark that native
chipselects is to be used. The value returned from of_get_named_gpio_flags in
this case is -EEXIST. By initializing cs_gpios and cs_gpio with -EEXIST, this
and only this errno will indicate to a spi controller driver that a native
chipselect is to be used.

Signed-off-by: Andreas Larsson <andreas@...sler.com>
---
 drivers/spi/spi.c       |    4 ++--
 include/linux/spi/spi.h |    7 +++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 6f1b717..7494bad 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -334,7 +334,7 @@ struct spi_device *spi_alloc_device(struct spi_master *master)
 	spi->dev.parent = &master->dev;
 	spi->dev.bus = &spi_bus_type;
 	spi->dev.release = spidev_release;
-	spi->cs_gpio = -EINVAL;
+	spi->cs_gpio = -EEXIST;
 	device_initialize(&spi->dev);
 	return spi;
 }
@@ -1097,7 +1097,7 @@ static int of_spi_register_master(struct spi_master *master)
 	}
 
 	for (i = 0; i < master->num_chipselect; i++)
-		cs[i] = -EINVAL;
+		cs[i] = -EEXIST;
 
 	for (i = 0; i < nb; i++)
 		cs[i] = of_get_named_gpio_flags(np, "cs-gpios", i, &flags[i]);
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 96b1055..0701882 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -58,7 +58,8 @@ extern struct bus_type spi_bus_type;
  * @modalias: Name of the driver to use with this device, or an alias
  *	for that name.  This appears in the sysfs "modalias" attribute
  *	for driver coldplugging, and in uevents used for hotplugging
- * @cs_gpio: Negative or gpio for chip select.
+ * @cs_gpio: Negative or gpio for chip select.  Set to -EEXIST when chipselect
+ *	should be handled natively by the controller driver
  * @cs_gpio_flags: of_gpio_flags corresponding to cs_gpio
  *
  * A @spi_device is used to interchange data between an SPI slave
@@ -262,7 +263,9 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
  * @unprepare_transfer_hardware: there are currently no more messages on the
  *	queue so the subsystem notifies the driver that it may relax the
  *	hardware by issuing this call
- * @cs_gpios: possible array of negative values or gpios for chip selects
+ * @cs_gpios: possible array of negative values or gpios for chip selects.  A
+ *	chipselect that should be handled natively by the controller driver is
+ *	set to -EEXIST.
  * @cs_gpio_flags: possible array of of_gpio_flags corresponding to cs_gpios
  *
  * Each SPI master controller can communicate with one or more @spi_device
-- 
1.7.0.4

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