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| author | Wolfram Sang <wsa+renesas@sang-engineering.com> | 2015-07-27 14:03:38 +0200 |
|---|---|---|
| committer | Wolfram Sang <wsa@the-dreams.de> | 2015-08-24 14:05:15 +0200 |
| commit | cfa0327b0d03091e0c47249c080e50e287be762d (patch) | |
| tree | 623f03aee6dc0bbdaada27b4f2cab5e4a7fd87fd /Documentation/i2c | |
| parent | i2c: take address space into account when checking for used addresses (diff) | |
| download | linux-cfa0327b0d03091e0c47249c080e50e287be762d.tar.xz linux-cfa0327b0d03091e0c47249c080e50e287be762d.zip | |
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-interface | 9 | ||||
| -rw-r--r-- | Documentation/i2c/ten-bit-addresses | 4 |
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. |