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| -rw-r--r-- | Documentation/driver-model/interface.txt | 129 |
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diff --git a/Documentation/driver-model/interface.txt b/Documentation/driver-model/interface.txt deleted file mode 100644 index c66912b..0000000 --- a/Documentation/driver-model/interface.txt +++ /dev/null @@ -1,129 +0,0 @@ - -Device Interfaces - -Introduction -~~~~~~~~~~~~ - -Device interfaces are the logical interfaces of device classes that correlate -directly to userspace interfaces, like device nodes. - -Each device class may have multiple interfaces through which you can -access the same device. An input device may support the mouse interface, -the 'evdev' interface, and the touchscreen interface. A SCSI disk would -support the disk interface, the SCSI generic interface, and possibly a raw -device interface. - -Device interfaces are registered with the class they belong to. As devices -are added to the class, they are added to each interface registered with -the class. The interface is responsible for determining whether the device -supports the interface or not. - - -Programming Interface -~~~~~~~~~~~~~~~~~~~~~ - -struct device_interface { - char * name; - rwlock_t lock; - u32 devnum; - struct device_class * devclass; - - struct list_head node; - struct driver_dir_entry dir; - - int (*add_device)(struct device *); - int (*add_device)(struct intf_data *); -}; - -int interface_register(struct device_interface *); -void interface_unregister(struct device_interface *); - - -An interface must specify the device class it belongs to. It is added -to that class's list of interfaces on registration. - - -Interfaces can be added to a device class at any time. Whenever it is -added, each device in the class is passed to the interface's -add_device callback. When an interface is removed, each device is -removed from the interface. - - -Devices -~~~~~~~ -Once a device is added to a device class, it is added to each -interface that is registered with the device class. The class -is expected to place a class-specific data structure in -struct device::class_data. The interface can use that (along with -other fields of struct device) to determine whether or not the driver -and/or device support that particular interface. - - -Data -~~~~ - -struct intf_data { - struct list_head node; - struct device_interface * intf; - struct device * dev; - u32 intf_num; -}; - -int interface_add_data(struct interface_data *); - -The interface is responsible for allocating and initializing a struct -intf_data and calling interface_add_data() to add it to the device's list -of interfaces it belongs to. This list will be iterated over when the device -is removed from the class (instead of all possible interfaces for a class). -This structure should probably be embedded in whatever per-device data -structure the interface is allocating anyway. - -Devices are enumerated within the interface. This happens in interface_add_data() -and the enumerated value is stored in the struct intf_data for that device. - -sysfs -~~~~~ -Each interface is given a directory in the directory of the device -class it belongs to: - -Interfaces get a directory in the class's directory as well: - - class/ - `-- input - |-- devices - |-- drivers - |-- mouse - `-- evdev - -When a device is added to the interface, a symlink is created 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 - | `-- usb:usb_mouse -> ../../../bus/drivers/usb_mouse/ - |-- mouse - | `-- 1 -> ../../../root/pci0/00:1f.0/usb_bus/00:1f.2-1:0/ - `-- evdev - `-- 1 -> ../../../root/pci0/00:1f.0/usb_bus/00:1f.2-1:0/ - - -Future Plans -~~~~~~~~~~~~ -A device interface is correlated directly with a userspace interface -for a device, specifically a device node. For instance, a SCSI disk -exposes at least two interfaces to userspace: the standard SCSI disk -interface and the SCSI generic interface. It might also export a raw -device interface. - -Many interfaces have a major number associated with them and each -device gets a minor number. Or, multiple interfaces might share one -major number, and each will receive a range of minor numbers (like in -the case of input devices). - -These major and minor numbers could be stored in the interface -structure. Major and minor allocations could happen when the interface -is registered with the class, or via a helper function. - |