From b5527a7766f0505dc72efe3cefe5e9dea826f611 Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Tue, 2 Mar 2010 12:23:42 +0100 Subject: i2c: Add SMBus alert support SMBus alert support. 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 based on preliminary work by David Brownell. The key difference between David's implementation and mine is that his was part of i2c-core, while mine is split into a separate, standalone module named i2c-smbus. The i2c-smbus module is meant to include support for all SMBus extensions to the I2C protocol in the future. The benefit of this approach is a zero cost for I2C bus segments which do not need SMBus alert support. Where David's implementation increased the size of struct i2c_adapter by 7% (40 bytes on i386), mine doesn't touch it. Where David's implementation added over 150 lines of code to i2c-core (+10%), mine doesn't touch it. The only change that touches all the users of the i2c subsystem is a new callback in struct i2c_driver (common to both implementations.) I seem to remember Trent was worried about the footprint of David'd implementation, hopefully mine addresses the issue. Signed-off-by: Jean Delvare Acked-by: Jonathan Cameron Cc: David Brownell Cc: Trent Piepho --- include/linux/i2c.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/linux/i2c.h') diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 02fc617..476abd0 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -152,6 +152,13 @@ struct i2c_driver { int (*suspend)(struct i2c_client *, pm_message_t mesg); int (*resume)(struct i2c_client *); + /* Alert callback, for example for the SMBus alert protocol. + * The format and meaning of the data value depends on the protocol. + * For the SMBus alert protocol, there is a single bit of data passed + * as the alert response's low bit ("event flag"). + */ + void (*alert)(struct i2c_client *, unsigned int data); + /* a ioctl like command that can be used to perform specific functions * with the device. */ -- cgit v1.1