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i2c: stub: Add support for banked register ranges

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Some chips implement banked register ranges. This allows implementing
more registers than the limited 8-bit address space originally allows.
In order to access a register on these chips, you must first select
the proper bank. Add support for this mechanism to the i2c-stub driver
so that such chips can be emulated. All the bank settings are passed
as module parameters.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Jean Delvare
2014-07-10 12:56:59 +02:00
committed by Wolfram Sang
parent 1dff59831b
commit 2408c17fce
2 changed files with 128 additions and 14 deletions
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Documentation/i2c/i2c-stub
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@@ -47,15 +47,18 @@ unsigned long functionality:
value 0x1f0000 would only enable the quick, byte and byte data
commands.
u8 bank_reg[10]
u8 bank_mask[10]
u8 bank_start[10]
u8 bank_end[10]:
Optional bank settings. They tell which bits in which register
select the active bank, as well as the range of banked registers.
CAVEATS:
If your target driver polls some byte or word waiting for it to change, the
stub could lock it up. Use i2cset to unlock it.
If the hardware for your driver has banked registers (e.g. Winbond sensors
chips) this module will not work well - although it could be extended to
support that pretty easily.
If you spam it hard enough, printk can be lossy. This module really wants
something like relayfs.