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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>
This commit is contained in:
Jean Delvare 2009-02-24 19:19:49 +01:00
parent a746b578d8
commit cd97f39b7c
3 changed files with 7 additions and 3 deletions
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6
drivers/i2c/i2c-dev.c
View File

@ -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

2
include/linux/i2c-dev.h
View File

@ -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)

2
include/linux/i2c.h
View File

@ -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 */