V4L/DVB (11671): v4l2: add v4l2_device_set_name()

Add a utility function that can be used to setup the v4l2_device's name
field in a standard manner.

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

Documentation/video4linux/v4l2-framework.txt

@@ -89,6 +89,11 @@ 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.
 
+You can use v4l2_device_set_name() to set the name based on a driver name and
+a driver-global atomic_t instance. This will generate names like ivtv0, ivtv1,
+etc. If the name ends with a digit, then it will insert a dash: cx18-0,
+cx18-1, etc. This function returns the instance number.
+
 The first 'dev' argument is normally the struct device pointer of a pci_dev,
 usb_interface or platform_device. It is rare for dev to be NULL, but it happens
 with ISA devices or when one device creates multiple PCI devices, thus making

drivers/media/video/v4l2-device.c

@@ -49,6 +49,22 @@ int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev)
 }
 EXPORT_SYMBOL_GPL(v4l2_device_register);
 
+int v4l2_device_set_name(struct v4l2_device *v4l2_dev, const char *basename,
+						atomic_t *instance)
+{
+	int num = atomic_inc_return(instance) - 1;
+	int len = strlen(basename);
+
+	if (basename[len - 1] >= '0' && basename[len - 1] <= '9')
+		snprintf(v4l2_dev->name, sizeof(v4l2_dev->name),
+				"%s-%d", basename, num);
+	else
+		snprintf(v4l2_dev->name, sizeof(v4l2_dev->name),
+				"%s%d", basename, num);
+	return num;
+}
+EXPORT_SYMBOL_GPL(v4l2_device_set_name);
+
 void v4l2_device_disconnect(struct v4l2_device *v4l2_dev)
 {
 	if (v4l2_dev->dev) {

include/media/v4l2-device.h

@@ -53,10 +53,31 @@ struct v4l2_device {
    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);
+
+/* Optional function to initialize the name field of struct v4l2_device using
+   the driver name and a driver-global atomic_t instance.
+   This function will increment the instance counter and returns the instance
+   value used in the name.
+
+   Example:
+
+   static atomic_t drv_instance = ATOMIC_INIT(0);
+
+   ...
+
+   instance = v4l2_device_set_name(&v4l2_dev, "foo", &drv_instance);
+
+   The first time this is called the name field will be set to foo0 and
+   this function returns 0. If the name ends with a digit (e.g. cx18),
+   then the name will be set to cx18-0 since cx180 looks really odd. */
+int v4l2_device_set_name(struct v4l2_device *v4l2_dev, const char *basename,
+						atomic_t *instance);
+
 /* Set v4l2_dev->dev to NULL. Call when the USB parent disconnects.
    Since the parent disappears this ensures that v4l2_dev doesn't have an
    invalid parent pointer. */
 void v4l2_device_disconnect(struct v4l2_device *v4l2_dev);
+
 /* Unregister all sub-devices and any other resources related to v4l2_dev. */
 void v4l2_device_unregister(struct v4l2_device *v4l2_dev);