Re: [PATCH] i2c-mpc: do not allow interruptions when waiting for I2C to complete

[Ben Dooks <ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>]

On Fri, Feb 06, 2009 at 08:00:37AM -0600, Timur Tabi wrote:
> The i2c_wait() function is using wait_event_interruptible_timeout() to wait for
> the I2C controller to signal that it has completed an I2C bus operation.  If
> the process that causes the I2C operation terminated abruptly, the wait will
> be interrupted, returning an error.  It is better to let the I2C operation
> finished before the process exits.
> 
> It is safe to use wait_event_timeout() instead, because the timeout will allow
> the process to exit if the I2C bus hangs.  It's also better to allow the
> I2C operation to finish, because unacknowledged I2C operations can cause the
> I2C bus to hang.
> 
> Signed-off-by: Timur Tabi <timur-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
Acked-by: Ben Dooks <ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>
> ---
> 
> A similar change should probably be done to i2c-cpm.c, and maybe all other
> I2C drivers.  Not many use wait_event_interruptible_timeout().
> 
>  drivers/i2c/busses/i2c-mpc.c |    9 +++------
>  1 files changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
> index a9a45fc..c0ace48 100644
> --- a/drivers/i2c/busses/i2c-mpc.c
> +++ b/drivers/i2c/busses/i2c-mpc.c
> @@ -70,7 +70,7 @@ static irqreturn_t mpc_i2c_isr(int irq, void *dev_id)
>  		/* Read again to allow register to stabilise */
>  		i2c->interrupt = readb(i2c->base + MPC_I2C_SR);
>  		writeb(0, i2c->base + MPC_I2C_SR);
> -		wake_up_interruptible(&i2c->queue);
> +		wake_up(&i2c->queue);
>  	}
>  	return IRQ_HANDLED;
>  }
> @@ -115,13 +115,10 @@ static int i2c_wait(struct mpc_i2c *i2c, unsigned timeout, int writing)
>  		writeb(0, i2c->base + MPC_I2C_SR);
>  	} else {
>  		/* Interrupt mode */
> -		result = wait_event_interruptible_timeout(i2c->queue,
> +		result = wait_event_timeout(i2c->queue,
>  			(i2c->interrupt & CSR_MIF), timeout * HZ);
>  
> -		if (unlikely(result < 0)) {
> -			pr_debug("I2C: wait interrupted\n");
> -			writeccr(i2c, 0);
> -		} else if (unlikely(!(i2c->interrupt & CSR_MIF))) {
> +		if (unlikely(!(i2c->interrupt & CSR_MIF))) {
>  			pr_debug("I2C: wait timeout\n");
>  			writeccr(i2c, 0);
>  			result = -ETIMEDOUT;
> -- 
> 1.5.5
> 
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-- 
Ben (ben-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org, http://www.fluff.org/)

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