From cfa0327b0d03091e0c47249c080e50e287be762d Mon Sep 17 00:00:00 2001 From: Wolfram Sang Date: Mon, 27 Jul 2015 14:03:38 +0200 Subject: i2c: support 10 bit and slave addresses in sysfs 'new_device' We now have seperate address spaces for 10 bit and we-are-slave clients. Update the sysfs device instantiation method to support these types by accepting the address offsets that are assigned to the extra address spaces. Update the documentation, too. Signed-off-by: Wolfram Sang Signed-off-by: Wolfram Sang --- Documentation/i2c/slave-interface | 9 ++++++--- Documentation/i2c/ten-bit-addresses | 4 ++++ 2 files changed, 10 insertions(+), 3 deletions(-) (limited to 'Documentation/i2c') diff --git a/Documentation/i2c/slave-interface b/Documentation/i2c/slave-interface index 2dee4e2d62df..61ed05cd9531 100644 --- a/Documentation/i2c/slave-interface +++ b/Documentation/i2c/slave-interface @@ -31,10 +31,13 @@ User manual =========== I2C slave backends behave like standard I2C clients. So, you can instantiate -them as described in the document 'instantiating-devices'. A quick example for -instantiating the slave-eeprom driver from userspace at address 0x64 on bus 1: +them as described in the document 'instantiating-devices'. The only difference +is that i2c slave backends have their own address space. So, you have to add +0x1000 to the address you would originally request. An example for +instantiating the slave-eeprom driver from userspace at the 7 bit address 0x64 +on bus 1: - # echo slave-24c02 0x64 > /sys/bus/i2c/devices/i2c-1/new_device + # echo slave-24c02 0x1064 > /sys/bus/i2c/devices/i2c-1/new_device Each backend should come with separate documentation to describe its specific behaviour and setup. diff --git a/Documentation/i2c/ten-bit-addresses b/Documentation/i2c/ten-bit-addresses index cdfe13901b99..7b2d11e53a49 100644 --- a/Documentation/i2c/ten-bit-addresses +++ b/Documentation/i2c/ten-bit-addresses @@ -2,6 +2,10 @@ The I2C protocol knows about two kinds of device addresses: normal 7 bit addresses, and an extended set of 10 bit addresses. The sets of addresses do not intersect: the 7 bit address 0x10 is not the same as the 10 bit address 0x10 (though a single device could respond to both of them). +To avoid ambiguity, the user sees 10 bit addresses mapped to a different +address space, namely 0xa000-0xa3ff. The leading 0xa (= 10) represents the +10 bit mode. This is used for creating device names in sysfs. It is also +needed when instantiating 10 bit devices via the new_device file in sysfs. I2C messages to and from 10-bit address devices have a different format. See the I2C specification for the details. -- cgit v1.2.3