On 08/28/2015 05:31 AM, Lee Jones wrote:

+static ssize_t rproc_state_write(struct file *filp, const char __user *userbuf,
+				 size_t count, loff_t *ppos)
+{
+	struct rproc *rproc = filp->private_data;
+	char buf[2];
+	int ret;
+
+	ret = copy_from_user(buf, userbuf, 1);
+	if (ret)
+		return -EFAULT;
+
+	switch (buf[0]) {
+	case '0':
+		rproc_shutdown(rproc);
+		break;
+	case '1':
+		ret = rproc_boot(rproc);
+		if (ret)
+			dev_warn(&rproc->dev, "Boot failed: %d\n", ret);
+		break;
+	default:
+		dev_err(&rproc->dev, "Unrecognised option: %x\n", buf[1]);
+		return -EINVAL;

This prints uninitialized kernel stack contents instead of what was
copied from user space.

Is the dev_err statement really necessary anyway?

+	}
+
+	return count;
+}

If rproc_boot fails, that should be reflected in the syscall result.

This interface is essentially exposing the remoteproc->power refcount to
user space; is that okay?  Seems like it makes it easy to underflow
remoteproc->power through successive shutdown calls.

The other debugfs interface in remoteproc that has a write method
(recovery) accepts more expressive string commands as opposed to 0/1.
It would be more consistent for this interface to take commands such as
"boot" and "shutdown" IMO.