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i2c: support 10 bit and slave addresses in sysfs 'new_device'

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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 <[email protected]>
Signed-off-by: Wolfram Sang <[email protected]>
This commit is contained in:
Wolfram Sang 2015-07-27 14:03:38 +02:00 • committed by Wolfram Sang
commit cfa0327b0d
3 changed files with 21 additions and 4 deletions
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9
Documentation/i2c/slave-interface
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@ -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.

4
Documentation/i2c/ten-bit-addresses
View file

@ -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.