Re: [PATCH] i2c-dev: Clarify the unit of ioctl I2C_TIMEOUT

[Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

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On Fri, Feb 20, 2009 at 01:21:37PM +0100, Jean Delvare wrote:
> 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-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>

Acked-by: Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>

(see minor nit below)

> ---
>  drivers/i2c/i2c-dev.c   |    6 +++++-
>  include/linux/i2c-dev.h |    2 +-
>  include/linux/i2c.h     |    2 +-
>  3 files changed, 7 insertions(+), 3 deletions(-)
> 
> --- linux-2.6.29-rc5.orig/drivers/i2c/i2c-dev.c	2009-01-06 20:24:44.000000000 +0100
> +++ linux-2.6.29-rc5/drivers/i2c/i2c-dev.c	2009-02-20 12:59:38.000000000 +0100
> @@ -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 *fi
>  		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.

Double space after * intended?

> +		 */
> +		client->adapter->timeout = msecs_to_jiffies(arg * 10);
>  		break;
>  	default:
>  		/* NOTE:  returning a fault code here could cause trouble
> --- linux-2.6.29-rc5.orig/include/linux/i2c-dev.h	2008-04-17 04:49:44.000000000 +0200
> +++ linux-2.6.29-rc5/include/linux/i2c-dev.h	2009-02-20 12:48:08.000000000 +0100
> @@ -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)
> --- linux-2.6.29-rc5.orig/include/linux/i2c.h	2009-01-29 08:27:20.000000000 +0100
> +++ linux-2.6.29-rc5/include/linux/i2c.h	2009-02-20 12:47:39.000000000 +0100
> @@ -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 */
>  
> 
> 
> -- 
> Jean Delvare
> --
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-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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