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Commit cd97f39b authored by Jean Delvare's avatar Jean Delvare
Browse files

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: default avatarJean Delvare <khali@linux-fr.org>
Acked-by: default avatarWolfram Sang <w.sang@pengutronix.de>
parent a746b578

drivers/i2c/i2c-dev.c

+5 −1
Original line number Diff line number Diff line
@@ -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

include/linux/i2c-dev.h

+1 −1
Original line number Diff line number Diff line
@@ -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)

include/linux/i2c.h

+1 −1
Original line number Diff line number Diff line
@@ -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 */