V4L/DVB (12543): v4l: introduce string control support.

The upcoming RDS encoder needs support for string controls. This patch
implements the core implementation.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 46 insertions, 19 deletions

diff --git a/drivers/media/video/v4l2-compat-ioctl32.c b/drivers/media/video/v4l2-compat-ioctl32.c
index 0056b115b42e..f788c41a3a5c 100644
--- a/drivers/media/video/v4l2-compat-ioctl32.c
+++ b/drivers/media/video/v4l2-compat-ioctl32.c
@@ -600,9 +600,35 @@ struct v4l2_ext_controls32 {
        compat_caddr_t controls; /* actually struct v4l2_ext_control32 * */
 };
 
+struct v4l2_ext_control32 {
+	__u32 id;
+	__u32 size;
+	__u32 reserved2[1];
+	union {
+		__s32 value;
+		__s64 value64;
+		compat_caddr_t string; /* actually char * */
+	};
+} __attribute__ ((packed));
+
+/* The following function really belong in v4l2-common, but that causes
+   a circular dependency between modules. We need to think about this, but
+   for now this will do. */
+
+/* Return non-zero if this control is a pointer type. Currently only
+ * type STRING is a pointer type.
+ *
+ * Note that there are currently no controls of this type, but at least the
+ * compat32 code is in place to properly handle such controls. Please
+ * remove this note once the first pointer controls are added. */
+static inline int ctrl_is_pointer(u32 id)
+{
+	return 0;
+}
+
 static int get_v4l2_ext_controls32(struct v4l2_ext_controls *kp, struct v4l2_ext_controls32 __user *up)
 {
-	struct v4l2_ext_control __user *ucontrols;
+	struct v4l2_ext_control32 __user *ucontrols;
 	struct v4l2_ext_control __user *kcontrols;
 	int n;
 	compat_caddr_t p;
@@ -626,15 +652,17 @@ static int get_v4l2_ext_controls32(struct v4l2_ext_controls *kp, struct v4l2_ext
 	kcontrols = compat_alloc_user_space(n * sizeof(struct v4l2_ext_control));
 	kp->controls = kcontrols;
 	while (--n >= 0) {
-		if (copy_in_user(&kcontrols->id, &ucontrols->id, sizeof(__u32)))
-			return -EFAULT;
-		if (copy_in_user(&kcontrols->reserved2, &ucontrols->reserved2, sizeof(ucontrols->reserved2)))
-			return -EFAULT;
-		/* Note: if the void * part of the union ever becomes relevant
-		   then we need to know the type of the control in order to do
-		   the right thing here. Luckily, that is not yet an issue. */
-		if (copy_in_user(&kcontrols->value, &ucontrols->value, sizeof(ucontrols->value)))
+		if (copy_in_user(kcontrols, ucontrols, sizeof(*kcontrols)))
 			return -EFAULT;
+		if (ctrl_is_pointer(kcontrols->id)) {
+			void __user *s;
+
+			if (get_user(p, &ucontrols->string))
+				return -EFAULT;
+			s = compat_ptr(p);
+			if (put_user(s, &kcontrols->string))
+				return -EFAULT;
+		}
 		ucontrols++;
 		kcontrols++;
 	}
@@ -643,7 +671,7 @@ static int get_v4l2_ext_controls32(struct v4l2_ext_controls *kp, struct v4l2_ext
 
 static int put_v4l2_ext_controls32(struct v4l2_ext_controls *kp, struct v4l2_ext_controls32 __user *up)
 {
-	struct v4l2_ext_control __user *ucontrols;
+	struct v4l2_ext_control32 __user *ucontrols;
 	struct v4l2_ext_control __user *kcontrols = kp->controls;
 	int n = kp->count;
 	compat_caddr_t p;
@@ -664,15 +692,14 @@ static int put_v4l2_ext_controls32(struct v4l2_ext_controls *kp, struct v4l2_ext
 		return -EFAULT;
 
 	while (--n >= 0) {
-		if (copy_in_user(&ucontrols->id, &kcontrols->id, sizeof(__u32)))
-			return -EFAULT;
-		if (copy_in_user(&ucontrols->reserved2, &kcontrols->reserved2,
-					sizeof(ucontrols->reserved2)))
-			return -EFAULT;
-		/* Note: if the void * part of the union ever becomes relevant
-		   then we need to know the type of the control in order to do
-		   the right thing here. Luckily, that is not yet an issue. */
-		if (copy_in_user(&ucontrols->value, &kcontrols->value, sizeof(ucontrols->value)))
+		unsigned size = sizeof(*ucontrols);
+
+		/* Do not modify the pointer when copying a pointer control.
+		   The contents of the pointer was changed, not the pointer
+		   itself. */
+		if (ctrl_is_pointer(kcontrols->id))
+			size -= sizeof(ucontrols->value64);
+		if (copy_in_user(ucontrols, kcontrols, size))
 			return -EFAULT;
 		ucontrols++;
 		kcontrols++;