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-smbus.h | 50 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/i2c.h | 7 +++++++ 2 files changed, 57 insertions(+) create mode 100644 include/linux/i2c-smbus.h (limited to 'include/linux') diff --git a/include/linux/i2c-smbus.h b/include/linux/i2c-smbus.h new file mode 100644 index 000000000000..63f57a8c8b31 --- /dev/null +++ b/include/linux/i2c-smbus.h @@ -0,0 +1,50 @@ +/* + * i2c-smbus.h - SMBus extensions to the I2C protocol + * + * Copyright (C) 2010 Jean Delvare + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#ifndef _LINUX_I2C_SMBUS_H +#define _LINUX_I2C_SMBUS_H + +#include + + +/** + * i2c_smbus_alert_setup - platform data for the smbus_alert i2c client + * @alert_edge_triggered: whether the alert interrupt is edge (1) or level (0) + * triggered + * @irq: IRQ number, if the smbus_alert driver should take care of interrupt + * handling + * + * If irq is not specified, the smbus_alert driver doesn't take care of + * interrupt handling. In that case it is up to the I2C bus driver to either + * handle the interrupts or to poll for alerts. + * + * If irq is specified then it it crucial that alert_edge_triggered is + * properly set. + */ +struct i2c_smbus_alert_setup { + unsigned int alert_edge_triggered:1; + int irq; +}; + +struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter, + struct i2c_smbus_alert_setup *setup); +int i2c_handle_smbus_alert(struct i2c_client *ara); + +#endif /* _LINUX_I2C_SMBUS_H */ diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 02fc617782ef..476abd09c921 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 v1.2.3 From 0c43ea544c1086fbbed5a6c99ea58eb64674ea8f Mon Sep 17 00:00:00 2001 From: Zhangfei Gao Date: Tue, 2 Mar 2010 12:23:49 +0100 Subject: i2c: Document the message size limit i2c_master_send & i2c_master_recv do not support more than 64 kb transfer, since msg.len is u16. Signed-off-by: Zhangfei Gao Signed-off-by: Jean Delvare --- Documentation/i2c/writing-clients | 5 +++-- drivers/i2c/i2c-core.c | 4 ++-- include/linux/i2c.h | 1 + 3 files changed, 6 insertions(+), 4 deletions(-) (limited to 'include/linux') diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients index 0a74603eb671..3219ee0dbfef 100644 --- a/Documentation/i2c/writing-clients +++ b/Documentation/i2c/writing-clients @@ -318,8 +318,9 @@ Plain I2C communication These routines read and write some bytes from/to a client. The client contains the i2c address, so you do not have to include it. The second parameter contains the bytes to read/write, the third the number of bytes -to read/write (must be less than the length of the buffer.) Returned is -the actual number of bytes read/written. +to read/write (must be less than the length of the buffer, also should be +less than 64k since msg.len is u16.) Returned is the actual number of bytes +read/written. int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num); diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index 4131698008b9..3202a86f420e 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -1183,7 +1183,7 @@ EXPORT_SYMBOL(i2c_transfer); * i2c_master_send - issue a single I2C message in master transmit mode * @client: Handle to slave device * @buf: Data that will be written to the slave - * @count: How many bytes to write + * @count: How many bytes to write, must be less than 64k since msg.len is u16 * * Returns negative errno, or else the number of bytes written. */ @@ -1210,7 +1210,7 @@ EXPORT_SYMBOL(i2c_master_send); * i2c_master_recv - issue a single I2C message in master receive mode * @client: Handle to slave device * @buf: Where to store data read from slave - * @count: How many bytes to read + * @count: How many bytes to read, must be less than 64k since msg.len is u16 * * Returns negative errno, or else the number of bytes read. */ diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 476abd09c921..0a5da639b327 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -53,6 +53,7 @@ struct i2c_board_info; * on a bus (or read from them). Apart from two basic transfer functions to * transmit one message at a time, a more complex version can be used to * transmit an arbitrary number of messages without interruption. + * @count must be be less than 64k since msg.len is u16. */ extern int i2c_master_send(struct i2c_client *client, const char *buf, int count); -- cgit v1.2.3