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diff --git a/Documentation/driver-api/driver-model/class.rst b/Documentation/driver-api/driver-model/class.rst deleted file mode 100644 index fff55b80e86a..000000000000 --- a/Documentation/driver-api/driver-model/class.rst +++ /dev/null @@ -1,149 +0,0 @@ -============== -Device Classes -============== - -Introduction -~~~~~~~~~~~~ -A device class describes a type of device, like an audio or network -device. The following device classes have been identified: - -<Insert List of Device Classes Here> - - -Each device class defines a set of semantics and a programming interface -that devices of that class adhere to. Device drivers are the -implementation of that programming interface for a particular device on -a particular bus. - -Device classes are agnostic with respect to what bus a device resides -on. - - -Programming Interface -~~~~~~~~~~~~~~~~~~~~~ -The device class structure looks like:: - - - typedef int (*devclass_add)(struct device *); - typedef void (*devclass_remove)(struct device *); - -See the kerneldoc for the struct class. - -A typical device class definition would look like:: - - struct device_class input_devclass = { - .name = "input", - .add_device = input_add_device, - .remove_device = input_remove_device, - }; - -Each device class structure should be exported in a header file so it -can be used by drivers, extensions and interfaces. - -Device classes are registered and unregistered with the core using:: - - int devclass_register(struct device_class * cls); - void devclass_unregister(struct device_class * cls); - - -Devices -~~~~~~~ -As devices are bound to drivers, they are added to the device class -that the driver belongs to. Before the driver model core, this would -typically happen during the driver's probe() callback, once the device -has been initialized. It now happens after the probe() callback -finishes from the core. - -The device is enumerated in the class. Each time a device is added to -the class, the class's devnum field is incremented and assigned to the -device. The field is never decremented, so if the device is removed -from the class and re-added, it will receive a different enumerated -value. - -The class is allowed to create a class-specific structure for the -device and store it in the device's class_data pointer. - -There is no list of devices in the device class. Each driver has a -list of devices that it supports. The device class has a list of -drivers of that particular class. To access all of the devices in the -class, iterate over the device lists of each driver in the class. - - -Device Drivers -~~~~~~~~~~~~~~ -Device drivers are added to device classes when they are registered -with the core. A driver specifies the class it belongs to by setting -the struct device_driver::devclass field. - - -sysfs directory structure -~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -There is a top-level sysfs directory named 'class'. - -Each class gets a directory in the class directory, along with two -default subdirectories:: - - class/ - `-- input - |-- devices - `-- drivers - - -Drivers registered with the class get a symlink in the drivers/ directory -that points to the driver's directory (under its bus directory):: - - class/ - `-- input - |-- devices - `-- drivers - `-- usb:usb_mouse -> ../../../bus/drivers/usb_mouse/ - - -Each device gets a symlink in the devices/ directory that points to the -device's directory in the physical hierarchy:: - - class/ - `-- input - |-- devices - | `-- 1 -> ../../../root/pci0/00:1f.0/usb_bus/00:1f.2-1:0/ - `-- drivers - - -Exporting Attributes -~~~~~~~~~~~~~~~~~~~~ - -:: - - struct devclass_attribute { - struct attribute attr; - ssize_t (*show)(struct device_class *, char * buf, size_t count, loff_t off); - ssize_t (*store)(struct device_class *, const char * buf, size_t count, loff_t off); - }; - -Class drivers can export attributes using the DEVCLASS_ATTR macro that works -similarly to the DEVICE_ATTR macro for devices. For example, a definition -like this:: - - static DEVCLASS_ATTR(debug,0644,show_debug,store_debug); - -is equivalent to declaring:: - - static devclass_attribute devclass_attr_debug; - -The bus driver can add and remove the attribute from the class's -sysfs directory using:: - - int devclass_create_file(struct device_class *, struct devclass_attribute *); - void devclass_remove_file(struct device_class *, struct devclass_attribute *); - -In the example above, the file will be named 'debug' in placed in the -class's directory in sysfs. - - -Interfaces -~~~~~~~~~~ -There may exist multiple mechanisms for accessing the same device of a -particular class type. Device interfaces describe these mechanisms. - -When a device is added to a device class, the core attempts to add it -to every interface that is registered with the device class. |