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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-02-16 04:17:51 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-02-16 04:17:51 +0400 |
| commit | 2d0ef4fb34b0462d84a2d87292144b9dad79c8d0 (patch) | |
| tree | 76e98a2ba1cae8baf1ce8e96f64b16aa98a41f2d /Documentation | |
| parent | 5a667a0c02f3d24eb82a44074d24524c17e1ad34 (diff) | |
| parent | fde1e418ab2c4269035f7f576e678b6ad3117d7d (diff) | |
| download | linux-2d0ef4fb34b0462d84a2d87292144b9dad79c8d0.tar.xz | |
Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux
Pull i2c fixes from Wolfram Sang:
"i2c has a bugfix and documentation improvements for you"
* 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
Documentation: i2c: mention ACPI method for instantiating devices
Documentation: i2c: describe devicetree method for instantiating devices
i2c: mv64xxx: refactor message start to ensure proper initialization
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/i2c/instantiating-devices | 41 |
1 files changed, 39 insertions, 2 deletions
diff --git a/Documentation/i2c/instantiating-devices b/Documentation/i2c/instantiating-devices index c70e7a7638d1..0d85ac1935b7 100644 --- a/Documentation/i2c/instantiating-devices +++ b/Documentation/i2c/instantiating-devices @@ -8,8 +8,8 @@ reason, the kernel code must instantiate I2C devices explicitly. There are several ways to achieve this, depending on the context and requirements. -Method 1: Declare the I2C devices by bus number ------------------------------------------------ +Method 1a: Declare the I2C devices by bus number +------------------------------------------------ This method is appropriate when the I2C bus is a system bus as is the case for many embedded systems. On such systems, each I2C bus has a number @@ -51,6 +51,43 @@ The devices will be automatically unbound and destroyed when the I2C bus they sit on goes away (if ever.) +Method 1b: Declare the I2C devices via devicetree +------------------------------------------------- + +This method has the same implications as method 1a. The declaration of I2C +devices is here done via devicetree as subnodes of the master controller. + +Example: + + i2c1: i2c@400a0000 { + /* ... master properties skipped ... */ + clock-frequency = <100000>; + + flash@50 { + compatible = "atmel,24c256"; + reg = <0x50>; + }; + + pca9532: gpio@60 { + compatible = "nxp,pca9532"; + gpio-controller; + #gpio-cells = <2>; + reg = <0x60>; + }; + }; + +Here, two devices are attached to the bus using a speed of 100kHz. For +additional properties which might be needed to set up the device, please refer +to its devicetree documentation in Documentation/devicetree/bindings/. + + +Method 1c: Declare the I2C devices via ACPI +------------------------------------------- + +ACPI can also describe I2C devices. There is special documentation for this +which is currently located at Documentation/acpi/enumeration.txt. + + Method 2: Instantiate the devices explicitly -------------------------------------------- |