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authorJean Delvare <khali@linux-fr.org>2009-02-24 19:19:49 +0100
committerJean Delvare <khali@linux-fr.org>2009-02-24 19:19:49 +0100
commitcd97f39b7cdf1c8a9c9f52865eec795b7f0c811d (patch)
tree010cd2255376a95120da810a1600bbd8d4d7d1c3
parenta746b578d8406b2db0e9f0d040061bc1f78433cf (diff)
i2c-dev: Clarify the unit of ioctl I2C_TIMEOUT
The unit in which user-space can set the bus timeout value is jiffies for historical reasons (back when HZ was always 100.) This is however not good because user-space doesn't know how long a jiffy lasts. The timeout value should instead be set in a fixed time unit. Given the original value of HZ, this unit should be 10 ms, for compatibility. Signed-off-by: Jean Delvare <khali@linux-fr.org> Acked-by: Wolfram Sang <w.sang@pengutronix.de>
-rw-r--r--drivers/i2c/i2c-dev.c6
-rw-r--r--include/linux/i2c-dev.h2
-rw-r--r--include/linux/i2c.h2
3 files changed, 7 insertions, 3 deletions
diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index c171988a9f5..7e13d2df9af 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -35,6 +35,7 @@
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include <linux/smp_lock.h>
+#include <linux/jiffies.h>
#include <asm/uaccess.h>
static struct i2c_driver i2cdev_driver;
@@ -422,7 +423,10 @@ static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
client->adapter->retries = arg;
break;
case I2C_TIMEOUT:
- client->adapter->timeout = arg;
+ /* For historical reasons, user-space sets the timeout
+ * value in units of 10 ms.
+ */
+ client->adapter->timeout = msecs_to_jiffies(arg * 10);
break;
default:
/* NOTE: returning a fault code here could cause trouble
diff --git a/include/linux/i2c-dev.h b/include/linux/i2c-dev.h
index 311315b56b6..fd53bfd2647 100644
--- a/include/linux/i2c-dev.h
+++ b/include/linux/i2c-dev.h
@@ -33,7 +33,7 @@
*/
#define I2C_RETRIES 0x0701 /* number of times a device address should
be polled when not acknowledging */
-#define I2C_TIMEOUT 0x0702 /* set timeout in jiffies - call with int */
+#define I2C_TIMEOUT 0x0702 /* set timeout in units of 10 ms */
/* NOTE: Slave address is 7 or 10 bits, but 10-bit addresses
* are NOT supported! (due to code brokenness)
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index fcfbfea3af7..c86c3b07604 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -361,7 +361,7 @@ struct i2c_adapter {
struct mutex bus_lock;
struct mutex clist_lock;
- int timeout;
+ int timeout; /* in jiffies */
int retries;
struct device dev; /* the adapter device */