mirror of https://gitee.com/openkylin/linux.git
23 lines
1.1 KiB
Plaintext
23 lines
1.1 KiB
Plaintext
|
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). You
|
||
|
|
select a 10 bit address by adding an extra byte after the address
|
||
|
|
byte:
|
||
|
|
S Addr7 Rd/Wr ....
|
||
|
|
becomes
|
||
|
|
S 11110 Addr10 Rd/Wr
|
||
|
|
S is the start bit, Rd/Wr the read/write bit, and if you count the number
|
||
|
|
of bits, you will see the there are 8 after the S bit for 7 bit addresses,
|
||
|
|
and 16 after the S bit for 10 bit addresses.
|
||
|
|
|
||
|
|
WARNING! The current 10 bit address support is EXPERIMENTAL. There are
|
||
|
|
several places in the code that will cause SEVERE PROBLEMS with 10 bit
|
||
|
|
addresses, even though there is some basic handling and hooks. Also,
|
||
|
|
almost no supported adapter handles the 10 bit addresses correctly.
|
||
|
|
|
||
|
|
As soon as a real 10 bit address device is spotted 'in the wild', we
|
||
|
|
can and will add proper support. Right now, 10 bit address devices
|
||
|
|
are defined by the I2C protocol, but we have never seen a single device
|
||
|
|
which supports them.
|