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>

drivers/media/video/v4l2-common.c

@@ -156,6 +156,8 @@ int v4l2_ctrl_check(struct v4l2_ext_control *ctrl, struct v4l2_queryctrl *qctrl,
 		return -EINVAL;
 	if (qctrl->flags & V4L2_CTRL_FLAG_GRABBED)
 		return -EBUSY;
+	if (qctrl->type == V4L2_CTRL_TYPE_STRING)
+		return 0;
 	if (qctrl->type == V4L2_CTRL_TYPE_BUTTON ||
 	    qctrl->type == V4L2_CTRL_TYPE_INTEGER64 ||
 	    qctrl->type == V4L2_CTRL_TYPE_CTRL_CLASS)

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++;

drivers/media/video/v4l2-ioctl.c

@@ -513,11 +513,12 @@ static inline void v4l_print_ext_ctrls(unsigned int cmd,
 	dbgarg(cmd, "");
 	printk(KERN_CONT "class=0x%x", c->ctrl_class);
 	for (i = 0; i < c->count; i++) {
-		if (show_vals)
+		if (show_vals && !c->controls[i].size)
 			printk(KERN_CONT " id/val=0x%x/0x%x",
 				c->controls[i].id, c->controls[i].value);
 		else
-			printk(KERN_CONT " id=0x%x", c->controls[i].id);
+			printk(KERN_CONT " id=0x%x,size=%u",
+				c->controls[i].id, c->controls[i].size);
 	}
 	printk(KERN_CONT "\n");
 };
@@ -528,10 +529,9 @@ static inline int check_ext_ctrls(struct v4l2_ext_controls *c, int allow_priv)
 
 	/* zero the reserved fields */
 	c->reserved[0] = c->reserved[1] = 0;
-	for (i = 0; i < c->count; i++) {
+	for (i = 0; i < c->count; i++)
 		c->controls[i].reserved2[0] = 0;
-		c->controls[i].reserved2[1] = 0;
-	}
+
 	/* V4L2_CID_PRIVATE_BASE cannot be used as control class
 	   when using extended controls.
 	   Only when passed in through VIDIOC_G_CTRL and VIDIOC_S_CTRL

include/linux/videodev2.h

@@ -167,6 +167,7 @@ enum v4l2_ctrl_type {
 	V4L2_CTRL_TYPE_BUTTON	     = 4,
 	V4L2_CTRL_TYPE_INTEGER64     = 5,
 	V4L2_CTRL_TYPE_CTRL_CLASS    = 6,
+	V4L2_CTRL_TYPE_STRING        = 7,
 };
 
 enum v4l2_tuner_type {
@@ -795,11 +796,12 @@ struct v4l2_control {
 
 struct v4l2_ext_control {
 	__u32 id;
-	__u32 reserved2[2];
+	__u32 size;
+	__u32 reserved2[1];
 	union {
 		__s32 value;
 		__s64 value64;
-		void *reserved;
+		char *string;
 	};
 } __attribute__ ((packed));