diff options
author | David Brownell <david-b@pacbell.net> | 2007-02-13 21:09:00 (GMT) |
---|---|---|
committer | Jean Delvare <khali@arrakis.delvare> | 2007-02-13 21:09:00 (GMT) |
commit | f37dd80ac2a67e4e4e921f99d34a1ceeb2488abb (patch) | |
tree | c845e39b24feac331a9a67d49e0b8061f52131b3 /Documentation/i2c | |
parent | b8d6f45b32f6fe72bf7304183275e99332544ce1 (diff) | |
download | linux-fsl-qoriq-f37dd80ac2a67e4e4e921f99d34a1ceeb2488abb.tar.xz |
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 <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Diffstat (limited to 'Documentation/i2c')
-rw-r--r-- | Documentation/i2c/porting-clients | 6 | ||||
-rw-r--r-- | Documentation/i2c/writing-clients | 58 |
2 files changed, 55 insertions, 9 deletions
diff --git a/Documentation/i2c/porting-clients b/Documentation/i2c/porting-clients index f03c2a0..ca272b2 100644 --- a/Documentation/i2c/porting-clients +++ b/Documentation/i2c/porting-clients @@ -129,6 +129,12 @@ Technical changes: structure, those name member should be initialized to a driver name string. i2c_driver itself has no name member anymore. +* [Driver model] Instead of shutdown or reboot notifiers, provide a + shutdown() method in your driver. + +* [Power management] Use the driver model suspend() and resume() + callbacks instead of the obsolete pm_register() calls. + Coding policy: * [Copyright] Use (C), not (c), for copyright. diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients index 3a057c8..fbcff96 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 ================ |