path: root/Documentation
diff options
authorLinus Torvalds <torvalds@linux-foundation.org>2014-02-15 16:17:51 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-02-15 16:17:51 -0800
commit2d0ef4fb34b0462d84a2d87292144b9dad79c8d0 (patch)
tree76e98a2ba1cae8baf1ce8e96f64b16aa98a41f2d /Documentation
parent5a667a0c02f3d24eb82a44074d24524c17e1ad34 (diff)
parentfde1e418ab2c4269035f7f576e678b6ad3117d7d (diff)
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')
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.
+ 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