cbb4451404
10-bit addresses overlap with traditional 7-bit addresses, leading in device name collisions. Add an arbitrary offset to 10-bit addresses to prevent this collision. The offset was chosen so that the address is still easily recognizable. Signed-off-by: Jean Delvare <khali@linux-fr.org> Acked-by: Wolfram Sang <w.sang@pengutronix.de>
24 lines
1.2 KiB
Text
24 lines
1.2 KiB
Text
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).
|
|
|
|
I2C messages to and from 10-bit address devices have a different format.
|
|
See the I2C specification for the details.
|
|
|
|
The current 10 bit address support is minimal. It should work, however
|
|
you can expect some problems along the way:
|
|
* Not all bus drivers support 10-bit addresses. Some don't because the
|
|
hardware doesn't support them (SMBus doesn't require 10-bit address
|
|
support for example), some don't because nobody bothered adding the
|
|
code (or it's there but not working properly.) Software implementation
|
|
(i2c-algo-bit) is known to work.
|
|
* Some optional features do not support 10-bit addresses. This is the
|
|
case of automatic detection and instantiation of devices by their,
|
|
drivers, for example.
|
|
* Many user-space packages (for example i2c-tools) lack support for
|
|
10-bit addresses.
|
|
|
|
Note that 10-bit address devices are still pretty rare, so the limitations
|
|
listed above could stay for a long time, maybe even forever if nobody
|
|
needs them to be fixed.
|