V4L/DVB (10643): v4l2-device: allow a NULL parent device when registering.

Some drivers (e.g. for ISA devices) have no parent device because there
is no associated bus driver. Allow the parent device to be NULL in
those cases when registering v4l2_device.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/video4linux/v4l2-framework.txt

@@ -84,12 +84,14 @@ You must register the device instance:
 	v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev);
 
 Registration will initialize the v4l2_device struct and link dev->driver_data
-to v4l2_dev. Registration will also set v4l2_dev->name to a value derived from
-dev (driver name followed by the bus_id, to be precise). You may change the
-name after registration if you want.
+to v4l2_dev. If v4l2_dev->name is empty then it will be set to a value derived
+from dev (driver name followed by the bus_id, to be precise). If you set it
+up before calling v4l2_device_register then it will be untouched. If dev is
+NULL, then you *must* setup v4l2_dev->name before calling v4l2_device_register.
 
 The first 'dev' argument is normally the struct device pointer of a pci_dev,
-usb_device or platform_device.
+usb_device or platform_device. It is rare for dev to be NULL, but it happens
+with ISA devices, for example.
 
 You unregister with:
 

drivers/media/video/v4l2-device.c

@@ -26,15 +26,24 @@
 
 int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev)
 {
-	if (dev == NULL || v4l2_dev == NULL)
+	if (v4l2_dev == NULL)
 		return -EINVAL;
-	/* Warn if we apparently re-register a device */
-	WARN_ON(dev_get_drvdata(dev) != NULL);
+
 	INIT_LIST_HEAD(&v4l2_dev->subdevs);
 	spin_lock_init(&v4l2_dev->lock);
 	v4l2_dev->dev = dev;
-	snprintf(v4l2_dev->name, sizeof(v4l2_dev->name), "%s %s",
+	if (dev == NULL) {
+		/* If dev == NULL, then name must be filled in by the caller */
+		WARN_ON(!v4l2_dev->name[0]);
+		return 0;
+	}
+
+	/* Set name to driver name + device name if it is empty. */
+	if (!v4l2_dev->name[0])
+		snprintf(v4l2_dev->name, sizeof(v4l2_dev->name), "%s %s",
 			dev->driver->name, dev_name(dev));
+	if (dev_get_drvdata(dev))
+		v4l2_warn(v4l2_dev, "Non-NULL drvdata on register\n");
 	dev_set_drvdata(dev, v4l2_dev);
 	return 0;
 }
@@ -44,10 +53,11 @@ void v4l2_device_unregister(struct v4l2_device *v4l2_dev)
 {
 	struct v4l2_subdev *sd, *next;
 
-	if (v4l2_dev == NULL || v4l2_dev->dev == NULL)
+	if (v4l2_dev == NULL)
 		return;
-	dev_set_drvdata(v4l2_dev->dev, NULL);
-	/* unregister subdevs */
+	if (v4l2_dev->dev)
+		dev_set_drvdata(v4l2_dev->dev, NULL);
+	/* Unregister subdevs */
 	list_for_each_entry_safe(sd, next, &v4l2_dev->subdevs, list)
 		v4l2_device_unregister_subdev(sd);
 
@@ -55,19 +65,20 @@ void v4l2_device_unregister(struct v4l2_device *v4l2_dev)
 }
 EXPORT_SYMBOL_GPL(v4l2_device_unregister);
 
-int v4l2_device_register_subdev(struct v4l2_device *dev, struct v4l2_subdev *sd)
+int v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
+						struct v4l2_subdev *sd)
 {
 	/* Check for valid input */
-	if (dev == NULL || sd == NULL || !sd->name[0])
+	if (v4l2_dev == NULL || sd == NULL || !sd->name[0])
 		return -EINVAL;
 	/* Warn if we apparently re-register a subdev */
 	WARN_ON(sd->dev != NULL);
 	if (!try_module_get(sd->owner))
 		return -ENODEV;
-	sd->dev = dev;
-	spin_lock(&dev->lock);
-	list_add_tail(&sd->list, &dev->subdevs);
-	spin_unlock(&dev->lock);
+	sd->dev = v4l2_dev;
+	spin_lock(&v4l2_dev->lock);
+	list_add_tail(&sd->list, &v4l2_dev->subdevs);
+	spin_unlock(&v4l2_dev->lock);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_device_register_subdev);

include/media/v4l2-device.h

@@ -33,7 +33,9 @@
 #define V4L2_DEVICE_NAME_SIZE (BUS_ID_SIZE + 16)
 
 struct v4l2_device {
-	/* dev->driver_data points to this struct */
+	/* dev->driver_data points to this struct.
+	   Note: dev might be NULL if there is no parent device
+	   as is the case with e.g. ISA devices. */
 	struct device *dev;
 	/* used to keep track of the registered subdevs */
 	struct list_head subdevs;
@@ -44,7 +46,9 @@ struct v4l2_device {
 	char name[V4L2_DEVICE_NAME_SIZE];
 };
 
-/* Initialize v4l2_dev and make dev->driver_data point to v4l2_dev */
+/* Initialize v4l2_dev and make dev->driver_data point to v4l2_dev.
+   dev may be NULL in rare cases (ISA devices). In that case you
+   must fill in the v4l2_dev->name field before calling this function. */
 int __must_check v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev);
 /* Set v4l2_dev->dev->driver_data to NULL and unregister all sub-devices */
 void v4l2_device_unregister(struct v4l2_device *v4l2_dev);
@@ -52,23 +56,24 @@ void v4l2_device_unregister(struct v4l2_device *v4l2_dev);
 /* Register a subdev with a v4l2 device. While registered the subdev module
    is marked as in-use. An error is returned if the module is no longer
    loaded when you attempt to register it. */
-int __must_check v4l2_device_register_subdev(struct v4l2_device *dev, struct v4l2_subdev *sd);
+int __must_check v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
+						struct v4l2_subdev *sd);
 /* Unregister a subdev with a v4l2 device. Can also be called if the subdev
    wasn't registered. In that case it will do nothing. */
 void v4l2_device_unregister_subdev(struct v4l2_subdev *sd);
 
 /* Iterate over all subdevs. */
-#define v4l2_device_for_each_subdev(sd, dev)				\
-	list_for_each_entry(sd, &(dev)->subdevs, list)
+#define v4l2_device_for_each_subdev(sd, v4l2_dev)			\
+	list_for_each_entry(sd, &(v4l2_dev)->subdevs, list)
 
 /* Call the specified callback for all subdevs matching the condition.
    Ignore any errors. Note that you cannot add or delete a subdev
    while walking the subdevs list. */
-#define __v4l2_device_call_subdevs(dev, cond, o, f, args...) 		\
+#define __v4l2_device_call_subdevs(v4l2_dev, cond, o, f, args...) 	\
 	do { 								\
 		struct v4l2_subdev *sd; 				\
 									\
-		list_for_each_entry(sd, &(dev)->subdevs, list)   	\
+		list_for_each_entry(sd, &(v4l2_dev)->subdevs, list)   	\
 			if ((cond) && sd->ops->o && sd->ops->o->f) 	\
 				sd->ops->o->f(sd , ##args); 		\
 	} while (0)
@@ -77,12 +82,12 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev *sd);
    If the callback returns an error other than 0 or -ENOIOCTLCMD, then
    return with that error code. Note that you cannot add or delete a
    subdev while walking the subdevs list. */
-#define __v4l2_device_call_subdevs_until_err(dev, cond, o, f, args...)  \
+#define __v4l2_device_call_subdevs_until_err(v4l2_dev, cond, o, f, args...) \
 ({ 									\
 	struct v4l2_subdev *sd; 					\
 	long err = 0; 							\
 									\
-	list_for_each_entry(sd, &(dev)->subdevs, list) { 		\
+	list_for_each_entry(sd, &(v4l2_dev)->subdevs, list) { 		\
 		if ((cond) && sd->ops->o && sd->ops->o->f) 		\
 			err = sd->ops->o->f(sd , ##args); 		\
 		if (err && err != -ENOIOCTLCMD)				\
@@ -94,16 +99,16 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev *sd);
 /* Call the specified callback for all subdevs matching grp_id (if 0, then
    match them all). Ignore any errors. Note that you cannot add or delete
    a subdev while walking the subdevs list. */
-#define v4l2_device_call_all(dev, grpid, o, f, args...) 		\
-	__v4l2_device_call_subdevs(dev, 				\
+#define v4l2_device_call_all(v4l2_dev, grpid, o, f, args...) 		\
+	__v4l2_device_call_subdevs(v4l2_dev, 				\
 			!(grpid) || sd->grp_id == (grpid), o, f , ##args)
 
 /* Call the specified callback for all subdevs matching grp_id (if 0, then
    match them all). If the callback returns an error other than 0 or
    -ENOIOCTLCMD, then return with that error code. Note that you cannot
    add or delete a subdev while walking the subdevs list. */
-#define v4l2_device_call_until_err(dev, grpid, o, f, args...) 		\
-	__v4l2_device_call_subdevs_until_err(dev,			\
+#define v4l2_device_call_until_err(v4l2_dev, grpid, o, f, args...) 	\
+	__v4l2_device_call_subdevs_until_err(v4l2_dev,			\
 		       !(grpid) || sd->grp_id == (grpid), o, f , ##args)
 
 #endif