i2c: Add SMBus alert support

[pandora-kernel.git] / Documentation / i2c / smbus-protocol

diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol
index 24bfb65..7c19d1a 100644 (file)
--- a/Documentation/i2c/smbus-protocol
+++ b/Documentation/i2c/smbus-protocol
@@ -109,8 +109,8 @@ specified through the Comm byte.
 S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] P
 
 
-SMBus Process Call
-==================
+SMBus Process Call:  i2c_smbus_process_call()
+=============================================
 
 This command selects a device register (through the Comm byte), sends
 16 bits of data to it, and reads 16 bits of data in return.
@@ -185,6 +185,22 @@ the protocol. All ARP communications use slave address 0x61 and
 require PEC checksums.
 
 
+SMBus Alert
+===========
+
+SMBus Alert was introduced in Revision 1.0 of the specification.
+
+The SMBus alert protocol allows several SMBus slave devices to share a
+single interrupt pin on the SMBus master, while still allowing the master
+to know which slave triggered the interrupt.
+
+This is implemented the following way in the Linux kernel:
+* I2C bus drivers which support SMBus alert should call
+  i2c_setup_smbus_alert() to setup SMBus alert support.
+* I2C drivers for devices which can trigger SMBus alerts should implement
+  the optional alert() callback.
+
+
 I2C Block Transactions
 ======================