[media] v4l2-dev.c: add debug sysfs entry

Since this could theoretically change the debug value while in the middle
of v4l2-ioctl.c, we make a copy of vfd->debug to ensure consistent debug
behavior.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/v4l2-dev.c

@@ -46,6 +46,29 @@ static ssize_t show_index(struct device *cd,
 	return sprintf(buf, "%i\n", vdev->index);
 }
 
+static ssize_t show_debug(struct device *cd,
+			 struct device_attribute *attr, char *buf)
+{
+	struct video_device *vdev = to_video_device(cd);
+
+	return sprintf(buf, "%i\n", vdev->debug);
+}
+
+static ssize_t set_debug(struct device *cd, struct device_attribute *attr,
+		   const char *buf, size_t len)
+{
+	struct video_device *vdev = to_video_device(cd);
+	int res = 0;
+	u16 value;
+
+	res = kstrtou16(buf, 0, &value);
+	if (res)
+		return res;
+
+	vdev->debug = value;
+	return len;
+}
+
 static ssize_t show_name(struct device *cd,
 			 struct device_attribute *attr, char *buf)
 {
@@ -56,6 +79,7 @@ static ssize_t show_name(struct device *cd,
 
 static struct device_attribute video_device_attrs[] = {
 	__ATTR(name, S_IRUGO, show_name, NULL),
+	__ATTR(debug, 0644, show_debug, set_debug),
 	__ATTR(index, S_IRUGO, show_index, NULL),
 	__ATTR_NULL
 };

drivers/media/video/v4l2-ioctl.c

@@ -1999,6 +1999,7 @@ static long __video_do_ioctl(struct file *file,
 	void *fh = file->private_data;
 	struct v4l2_fh *vfh = NULL;
 	int use_fh_prio = 0;
+	int debug = vfd->debug;
 	long ret = -ENOTTY;
 
 	if (ops == NULL) {
@@ -2032,7 +2033,7 @@ static long __video_do_ioctl(struct file *file,
 	}
 
 	write_only = _IOC_DIR(cmd) == _IOC_WRITE;
-	if (write_only && vfd->debug > V4L2_DEBUG_IOCTL) {
+	if (write_only && debug > V4L2_DEBUG_IOCTL) {
 		v4l_print_ioctl(vfd->name, cmd);
 		pr_cont(": ");
 		info->debug(arg, write_only);
@@ -2054,8 +2055,8 @@ static long __video_do_ioctl(struct file *file,
 	}
 
 done:
-	if (vfd->debug) {
-		if (write_only && vfd->debug > V4L2_DEBUG_IOCTL) {
+	if (debug) {
+		if (write_only && debug > V4L2_DEBUG_IOCTL) {
 			if (ret < 0)
 				printk(KERN_DEBUG "%s: error %ld\n",
 					video_device_node_name(vfd), ret);
@@ -2064,7 +2065,7 @@ static long __video_do_ioctl(struct file *file,
 		v4l_print_ioctl(vfd->name, cmd);
 		if (ret < 0)
 			pr_cont(": error %ld\n", ret);
-		else if (vfd->debug == V4L2_DEBUG_IOCTL)
+		else if (debug == V4L2_DEBUG_IOCTL)
 			pr_cont("\n");
 		else if (_IOC_DIR(cmd) == _IOC_NONE)
 			info->debug(arg, write_only);