Re: [PATCH 3/3] powerpc/fsl: add MPIC timer wakeup support

On 03/19/2013 01:25:42 AM, Wang Dongsheng-B40534 wrote:

quoted

-----Original Message-----
From: Wood Scott-B07421
Sent: Tuesday, March 19, 2013 8:31 AM
To: Wang Dongsheng-B40534
Cc: Gala Kumar-B11780; linuxppc-dev@lists.ozlabs.org; Wang =20

Dongsheng-

quoted

B40534; Zhao Chenhui-B35336; Li Yang-R58472
Subject: Re: [PATCH 3/3] powerpc/fsl: add MPIC timer wakeup support

On 03/08/2013 01:38:47 AM, Wang Dongsheng wrote:

quoted

+static ssize_t fsl_timer_wakeup_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf,
+				size_t count)
+{
+	struct timeval interval;
+	int ret;
+
+	interval.tv_usec =3D 0;
+	if (kstrtol(buf, 0, &interval.tv_sec))
+		return -EINVAL;

I don't think the buffer will NUL-terminated...  Ordinarily =20

there'll be

quoted

an LF terminator, but you can't rely on that (many other sysfs =20

attributes

quoted

seem to, though...).

I think we don't need to care about LF terminator.
The kstrtol--> _kstrtoull has been done.

My point is, what happens if userspace passes in a buffer that has no =20
terminator of any sort?  kstrtol will continue reading beyond the end =20
of the buffer.

quoted

quoted

+	mutex_lock(&sysfs_lock);
+
+	if (fsl_wakeup->timer && !interval.tv_sec) {
+		disable_irq_wake(fsl_wakeup->timer->irq);
+		mpic_free_timer(fsl_wakeup->timer);
+		fsl_wakeup->timer =3D NULL;
+		mutex_unlock(&sysfs_lock);
+
+		return count;
+	}
+
+	if (fsl_wakeup->timer) {
+		mutex_unlock(&sysfs_lock);
+		return -EBUSY;
+	}

So to change an already-set timer you have to set it to zero and =20

then to

quoted

what you want?  Why not just do:

	if (fsl_wakeup->timer) {
		disable_irq_wake(...);
		mpic_free_timer(...);
		fsl_wakeup_timer =3D NULL;
	}

	if (!interval.tv_sec) {
		mutex_unlock(&sysfs_lock);
		return count;
	}

You can't break up the it.
if echo zero the code will cancel the timer that is currently running.
Not echo non-zero value just zero to cancel.

Echoing a nonzero value wouldn't just be to cancel, it would be to set =20
a new timer after cancelling the old.

quoted

quoted

+	for (i =3D 0; mpic_attributes[i]; i++) {
+		ret =3D device_create_file(mpic_subsys.dev_root,
+					mpic_attributes[i]);
+		if (ret)
+			goto err2;
+	}

Is this code ever going to register more than one?

No, just one. I only keep the style here.
If you don't think it's necessary I can remove this loop.

I don't think it's necessary.

-Scott=