> On Tue, 14 Oct 2008 14:21:50 +0530 "Madhusudhan Chikkature" <madhu.cr@xxxxxx> wrote:
>
> ----- Original Message -----
> From: "Andrew Morton" <akpm@xxxxxxxxxxxxxxxxxxxx>
> To: "Madhusudhan Chikkature" <madhu.cr@xxxxxx>
> Cc: <gadiyar@xxxxxx>; <johnpol@xxxxxxxxxxx>; <linux-kernel@xxxxxxxxxxxxxxx>; <linux-omap@xxxxxxxxxxxxxxx>
> Sent: Monday, October 13, 2008 9:23 PM
> Subject: Re: [PATCH 1/5] HDQ Driver for OMAP2430/3430
>
>
> >> On Mon, 13 Oct 2008 18:55:43 +0530 "Madhusudhan Chikkature" <madhu.cr@xxxxxx> wrote:
> >>
> >> ----- Original Message -----
> >> From: "Andrew Morton" <akpm@xxxxxxxxxxxxxxxxxxxx>
> >> To: "Gadiyar, Anand" <gadiyar@xxxxxx>
> >> Cc: <johnpol@xxxxxxxxxxx>; <linux-kernel@xxxxxxxxxxxxxxx>; <linux-omap@xxxxxxxxxxxxxxx>; <madhu.cr@xxxxxx>
> >> Sent: Saturday, October 11, 2008 2:08 AM
> >> Subject: Re: [PATCH 1/5] HDQ Driver for OMAP2430/3430
> >>
> >>
> >> >> + /* set the GO bit */
> >> >> + hdq_reg_merge(hdq_data, OMAP_HDQ_CTRL_STATUS, OMAP_HDQ_CTRL_STATUS_GO,
> >> >> + OMAP_HDQ_CTRL_STATUS_DIR | OMAP_HDQ_CTRL_STATUS_GO);
> >> >> + /* wait for the TXCOMPLETE bit */
> >> >> + ret = wait_event_interruptible_timeout(hdq_wait_queue,
> >> >> + hdq_data->hdq_irqstatus, OMAP_HDQ_TIMEOUT);
> >> >> + if (ret < 0) {
> >> >> + dev_dbg(hdq_data->dev, "wait interrupted");
> >> >> + return -EINTR;
> >> >> + }
> >> >
> >> > Is this desirable? The user hits ^C and the driver bails out?
> >> >
> >> > I assume so, but was this tested?
> >>
> >> Andrew, What is the test scenario you mean here? A user hitting ^C when the driver is waiting for the TXCOMPLETE bit?
> >
> > Yes.
> >
>
> Yes. It is desired to return an error if the condition in the wait is not met. I need to change the check for return value to check for zero and neg value.
>
> I spent some time to test this perticular scenario.I could not really see any impact of hitting ^C when an application is
> transfering data in the background. When the h/w is programmed to transfer data and the driver issues a wait, I see that
> TXCOMPLETE interrupt comes immediately and wakes up as expected.
>
> So guess I am unable to hit ^C exactly when the driver is waiting in wait_event_interruptible_timeout(before the condition
> is met) for it to catch the signal. Is it generally suggested to use wait_event_timeout so that ^C signal is not caught?
>
I think it's reasonable to permit the driver's operations to be interrupted
in this manner. It's done in quite a few other places. But the problem is
actually *testing* it.
I guess one could do a whitebox-style test. Add new code like:
{
static int x;
if (!(x++ % 1000)) {
printk("hit ^c now\n");
msleep(2000);
}
}
in the right place.
Tricky.
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