spi/spidev: Add 32 bit compat ioctl()

Add the compat_ioctl for operations on /dev/spi* so that 32 bit
userspace applications can access SPI. As far as I can see all data
structure are already prepared for that, so no additional conversion has
to be done.

My use case is MIPS with N32 userspace ABI and toolchain, and that was
also the platform where I tested it successfully (Cavium Octeon).

Signed-off-by: Bernhard Walle <walle@corscience.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/spidev.c

@@ -30,6 +30,7 @@
 #include <linux/errno.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/compat.h>
 
 #include <linux/spi/spi.h>
 #include <linux/spi/spidev.h>
@@ -471,6 +472,16 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	return retval;
 }
 
+#ifdef CONFIG_COMPAT
+static long
+spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
+}
+#else
+#define spidev_compat_ioctl NULL
+#endif /* CONFIG_COMPAT */
+
 static int spidev_open(struct inode *inode, struct file *filp)
 {
 	struct spidev_data	*spidev;
@@ -543,6 +554,7 @@ static const struct file_operations spidev_fops = {
 	.write =	spidev_write,
 	.read =		spidev_read,
 	.unlocked_ioctl = spidev_ioctl,
+	.compat_ioctl = spidev_compat_ioctl,
 	.open =		spidev_open,
 	.release =	spidev_release,
 	.llseek =	no_llseek,