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authorWolfram Sang <wsa+renesas@sang-engineering.com>2015-07-27 15:03:38 +0300
committerWolfram Sang <wsa@the-dreams.de>2015-08-24 15:05:15 +0300
commitcfa0327b0d03091e0c47249c080e50e287be762d (patch)
tree623f03aee6dc0bbdaada27b4f2cab5e4a7fd87fd /Documentation/i2c
parent9bccc70a127cfe2a13e34d6b6e7300caae113f8f (diff)
downloadlinux-cfa0327b0d03091e0c47249c080e50e287be762d.tar.xz
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 <wsa+renesas@sang-engineering.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'Documentation/i2c')
-rw-r--r--Documentation/i2c/slave-interface9
-rw-r--r--Documentation/i2c/ten-bit-addresses4
2 files changed, 10 insertions, 3 deletions
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.