linux/Documentation/i2c/ten-bit-addresses
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   1The I2C protocol knows about two kinds of device addresses: normal 7 bit
   2addresses, and an extended set of 10 bit addresses. The sets of addresses
   3do not intersect: the 7 bit address 0x10 is not the same as the 10 bit
   4address 0x10 (though a single device could respond to both of them).
   5
   6I2C messages to and from 10-bit address devices have a different format.
   7See the I2C specification for the details.
   8
   9The current 10 bit address support is minimal. It should work, however
  10you can expect some problems along the way:
  11* Not all bus drivers support 10-bit addresses. Some don't because the
  12  hardware doesn't support them (SMBus doesn't require 10-bit address
  13  support for example), some don't because nobody bothered adding the
  14  code (or it's there but not working properly.) Software implementation
  15  (i2c-algo-bit) is known to work.
  16* Some optional features do not support 10-bit addresses. This is the
  17  case of automatic detection and instantiation of devices by their,
  18  drivers, for example.
  19* Many user-space packages (for example i2c-tools) lack support for
  20  10-bit addresses.
  21
  22Note that 10-bit address devices are still pretty rare, so the limitations
  23listed above could stay for a long time, maybe even forever if nobody
  24needs them to be fixed.
  25
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