[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>

2 files changed, 29 insertions, 4 deletions

diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index 83dbb2ddff10..c2122e53f051 100644
--- a/drivers/media/video/v4l2-dev.c
+++ b/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
 };
diff --git a/drivers/media/video/v4l2-ioctl.c b/drivers/media/video/v4l2-ioctl.c
index 9ded54b16e88..273c6d7bef65 100644
--- a/drivers/media/video/v4l2-ioctl.c
+++ b/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 @@ done:
                 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);