Merge branch 'driver-core-linus' of... (8733cb29) · Commits · e / devices / android_kernel_xiaomi_markw

Documentation/driver-model/interface.txt

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		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.

MAINTAINERS

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		DRIVER CORE, KOBJECTS, DEBUGFS AND SYSFS
		M: Greg Kroah-Hartman <gregkh@suse.de>
		T: quilt kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/
		T: git git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core-2.6.git
		S: Supported
		F: Documentation/kobject.txt
		F: drivers/base/

drivers/uio/uio.c

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		@@ -3,7 +3,7 @@
		*
		* Copyright(C) 2005, Benedikt Spranger <b.spranger@linutronix.de>
		* Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
		* Copyright(C) 2006, Hans J. Koch <hjk@linutronix.de>
		* Copyright(C) 2006, Hans J. Koch <hjk@hansjkoch.de>
		* Copyright(C) 2006, Greg Kroah-Hartman <greg@kroah.com>
		*
		* Userspace IO

drivers/uio/uio_cif.c

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		/*
		* UIO Hilscher CIF card driver
		*
		* (C) 2007 Hans J. Koch <hjk@linutronix.de>
		* (C) 2007 Hans J. Koch <hjk@hansjkoch.de>
		* Original code (C) 2005 Benedikt Spranger <b.spranger@linutronix.de>
		*
		* Licensed under GPL version 2 only.

drivers/uio/uio_netx.c

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		* UIO driver for Hilscher NetX based fieldbus cards (cifX, comX).
		* See http://www.hilscher.com for details.
		*
		* (C) 2007 Hans J. Koch <hjk@linutronix.de>
		* (C) 2007 Hans J. Koch <hjk@hansjkoch.de>
		* (C) 2008 Manuel Traut <manut@linutronix.de>
		*
		* Licensed under GPL version 2 only.