!Edrivers/spi/spi.c
</chapter>
+ <chapter id="i2c">
+ <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
+
+ <para>
+ I<superscript>2</superscript>C (or without fancy typography, "I2C")
+ is an acronym for the "Inter-IC" bus, a simple bus protocol which is
+ widely used where low data rate communications suffice.
+ Since it's also a licensed trademark, some vendors use another
+ name (such as "Two-Wire Interface", TWI) for the same bus.
+ I2C only needs two signals (SCL for clock, SDA for data), conserving
+ board real estate and minimizing signal quality issues.
+ Most I2C devices use seven bit addresses, and bus speeds of up
+ to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
+ found wide use.
+ I2C is a multi-master bus; open drain signaling is used to
+ arbitrate between masters, as well as to handshake and to
+ synchronize clocks from slower clients.
+ </para>
+
+ <para>
+ The Linux I2C programming interfaces support only the master
+ side of bus interactions, not the slave side.
+ The programming interface is structured around two kinds of driver,
+ and two kinds of device.
+ An I2C "Adapter Driver" abstracts the controller hardware; it binds
+ to a physical device (perhaps a PCI device or platform_device) and
+ exposes a <structname>struct i2c_adapter</structname> representing
+ each I2C bus segment it manages.
+ On each I2C bus segment will be I2C devices represented by a
+ <structname>struct i2c_client</structname>. Those devices will
+ be bound to a <structname>struct i2c_driver</structname>,
+ which should follow the standard Linux driver model.
+ (At this writing, a legacy model is more widely used.)
+ There are functions to perform various I2C protocol operations; at
+ this writing all such functions are usable only from task context.
+ </para>
+
+ <para>
+ The System Management Bus (SMBus) is a sibling protocol. Most SMBus
+ systems are also I2C conformant. The electrical constraints are
+ tighter for SMBus, and it standardizes particular protocol messages
+ and idioms. Controllers that support I2C can also support most
+ SMBus operations, but SMBus controllers don't support all the protocol
+ options that an I2C controller will.
+ There are functions to perform various SMBus protocol operations,
+ either using I2C primitives or by issuing SMBus commands to
+ i2c_adapter devices which don't support those I2C operations.
+ </para>
+
+!Iinclude/linux/i2c.h
+!Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
+!Edrivers/i2c/i2c-core.c
+ </chapter>
+
<chapter id="splice">
<title>splice API</title>
<para>)
!Ffs/splice.c
</chapter>
+
</book>
* i2c_new_device - instantiate an i2c device for use with a new style driver
* @adap: the adapter managing the device
* @info: describes one I2C device; bus_num is ignored
+ * Context: can sleep
*
* Create a device to work with a new style i2c driver, where binding is
* handled through driver model probe()/remove() methods. This call is not
/**
* i2c_unregister_device - reverse effect of i2c_new_device()
* @client: value returned from i2c_new_device()
+ * Context: can sleep
*/
void i2c_unregister_device(struct i2c_client *client)
{
/**
* i2c_add_adapter - declare i2c adapter, use dynamic bus number
* @adapter: the adapter to add
+ * Context: can sleep
*
* This routine is used to declare an I2C adapter when its bus number
* doesn't matter. Examples: for I2C adapters dynamically added by
/**
* i2c_add_numbered_adapter - declare i2c adapter, use static bus number
* @adap: the adapter to register (with adap->nr initialized)
+ * Context: can sleep
*
* This routine is used to declare an I2C adapter when its bus number
* matters. Example: for I2C adapters from system-on-chip CPUs, or
}
EXPORT_SYMBOL_GPL(i2c_add_numbered_adapter);
+/**
+ * i2c_del_adapter - unregister I2C adapter
+ * @adap: the adapter being unregistered
+ * Context: can sleep
+ *
+ * This unregisters an I2C adapter which was previously registered
+ * by @i2c_add_adapter or @i2c_add_numbered_adapter.
+ */
int i2c_del_adapter(struct i2c_adapter *adap)
{
struct list_head *item, *_n;
/**
* i2c_del_driver - unregister I2C driver
* @driver: the driver being unregistered
+ * Context: can sleep
*/
void i2c_del_driver(struct i2c_driver *driver)
{
/**
* struct i2c_client - represent an I2C slave device
+ * @flags: I2C_CLIENT_TEN indicates the device uses a ten bit chip address;
+ * I2C_CLIENT_PEC indicates it uses SMBus Packet Error Checking
* @addr: Address used on the I2C bus connected to the parent adapter.
* @name: Indicates the type of the device, usually a chip name that's
* generic enough to hide second-sourcing and compatible revisions.
+ * @adapter: manages the bus segment hosting this I2C device
* @dev: Driver model device node for the slave.
+ * @irq: indicates the IRQ generated by this device (if any)
* @driver_name: Identifies new-style driver used with this device; also
* used as the module name for hotplug/coldplug modprobe support.
*
* An i2c_client identifies a single device (i.e. chip) connected to an
- * i2c bus. The behaviour is defined by the routines of the driver.
+ * i2c bus. The behaviour exposed to Linux is defined by the driver
+ * managing the device.
*/
struct i2c_client {
unsigned short flags; /* div., see below */
* @addr: stored in i2c_client.addr
* @platform_data: stored in i2c_client.dev.platform_data
* @irq: stored in i2c_client.irq
-
+ *
* I2C doesn't actually support hardware probing, although controllers and
* devices may be able to use I2C_SMBUS_QUICK to tell whether or not there's
* a device at a given address. Drivers commonly need more information than
* i2c_board_info is used to build tables of information listing I2C devices
* that are present. This information is used to grow the driver model tree
* for "new style" I2C drivers. For mainboards this is done statically using
- * i2c_register_board_info(), where @bus_num represents an adapter that isn't
+ * i2c_register_board_info(); bus numbers identify adapters that aren't
* yet available. For add-on boards, i2c_new_device() does this dynamically
* with the adapter already known.
*/
projects / linux-2.6 / commitdiff