Revision a45dc2d2b8d1afa57c91dcfac224e50ffcd3f805 authored by Benny Halevy on 13 September 2010, 19:32:19 UTC, committed by Jens Axboe on 21 September 2010, 09:49:17 UTC
This bug was introduced in 7b6d91daee5cac6402186ff224c3af39d79f4a0e "block: unify flags for struct bio and struct request" Cc: Boaz Harrosh <bharrosh@panasas.com> Signed-off-by: Benny Halevy <bhalevy@panasas.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
1 parent b0722cb
ten-bit-addresses
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.
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