From f37dd80ac2a67e4e4e921f99d34a1ceeb2488abb Mon Sep 17 00:00:00 2001 From: David Brownell Date: Tue, 13 Feb 2007 22:09:00 +0100 Subject: i2c: Add driver suspend/resume/shutdown support Driver model updates for the I2C core: - Add new suspend(), resume(), and shutdown() methods. Use them in the standard driver model style; document them. - Minor doc updates to highlight zero-initialized fields in drivers, and the driver model accessors for "clientdata". If any i2c drivers were previously using the old suspend/resume calls in "struct driver", they were getting warning messages ... and will now no longer work. Other than that, this patch changes no behaviors; and it lets I2C drivers use conventional PM and shutdown support. Signed-off-by: David Brownell Signed-off-by: Jean Delvare --- Documentation/i2c/writing-clients | 58 +++++++++++++++++++++++++++++++++------ 1 file changed, 49 insertions(+), 9 deletions(-) (limited to 'Documentation/i2c/writing-clients') diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients index 3a057c8e550..fbcff96f4ca 100644 --- a/Documentation/i2c/writing-clients +++ b/Documentation/i2c/writing-clients @@ -21,20 +21,26 @@ The driver structure Usually, you will implement a single driver structure, and instantiate all clients from it. Remember, a driver structure contains general access -routines, a client structure specific information like the actual I2C -address. +routines, and should be zero-initialized except for fields with data you +provide. A client structure holds device-specific information like the +driver model device node, and its I2C address. static struct i2c_driver foo_driver = { .driver = { .name = "foo", }, - .attach_adapter = &foo_attach_adapter, - .detach_client = &foo_detach_client, - .command = &foo_command /* may be NULL */ + .attach_adapter = foo_attach_adapter, + .detach_client = foo_detach_client, + .shutdown = foo_shutdown, /* optional */ + .suspend = foo_suspend, /* optional */ + .resume = foo_resume, /* optional */ + .command = foo_command, /* optional */ } -The name field must match the driver name, including the case. It must not -contain spaces, and may be up to 31 characters long. +The name field is the driver name, and must not contain spaces. It +should match the module name (if the driver can be compiled as a module), +although you can use MODULE_ALIAS (passing "foo" in this example) to add +another name for the module. All other fields are for call-back functions which will be explained below. @@ -43,11 +49,18 @@ below. Extra client data ================= -The client structure has a special `data' field that can point to any -structure at all. You can use this to keep client-specific data. You +Each client structure has a special `data' field that can point to any +structure at all. You should use this to keep device-specific data, +especially in drivers that handle multiple I2C or SMBUS devices. You do not always need this, but especially for `sensors' drivers, it can be very useful. + /* store the value */ + void i2c_set_clientdata(struct i2c_client *client, void *data); + + /* retrieve the value */ + void *i2c_get_clientdata(struct i2c_client *client); + An example structure is below. struct foo_data { @@ -493,6 +506,33 @@ by `__init_data'. Hose functions and structures can be removed after kernel booting (or module loading) is completed. +Power Management +================ + +If your I2C device needs special handling when entering a system low +power state -- like putting a transceiver into a low power mode, or +activating a system wakeup mechanism -- do that in the suspend() method. +The resume() method should reverse what the suspend() method does. + +These are standard driver model calls, and they work just like they +would for any other driver stack. The calls can sleep, and can use +I2C messaging to the device being suspended or resumed (since their +parent I2C adapter is active when these calls are issued, and IRQs +are still enabled). + + +System Shutdown +=============== + +If your I2C device needs special handling when the system shuts down +or reboots (including kexec) -- like turning something off -- use a +shutdown() method. + +Again, this is a standard driver model call, working just like it +would for any other driver stack: the calls can sleep, and can use +I2C messaging. + + Command function ================ -- cgit v1.2.3