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i2c: gpio: fault-injector: add incomplete_write_byte

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Add another injector for an incomplete transfer. As mentioned in the
docs, this one is important to check bus recovery algorithms with it.
Otherwise random data may be sent to devices!

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Wolfram Sang
2018-06-29 11:12:47 +02:00
committed by Wolfram Sang
parent 16d55daa56
commit bbe899700a
2 changed files with 40 additions and 0 deletions
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19
Documentation/i2c/gpio-fault-injection
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@@ -60,3 +60,22 @@ above, the bus master under test should detect this condition and try a bus
recovery. This time, however, it should succeed and the device should release
SDA after toggling SCL.
"incomplete_write_byte"
-----------------------
Similar to above, this file is write only and you need to write the address of
an existing I2C client device to it.
The injector will again stop at one ACK phase, so the device will keep SDA low
because it acknowledges data. However, there are two differences compared to
'incomplete_address_phase':
a) the message sent out will be a write message
b) after the address byte, a 0x00 byte will be transferred. Then, stop at ACK.
This is a highly delicate state, the device is set up to write any data to
register 0x00 (if it has registers) when further clock pulses happen on SCL.
This is why bus recovery (up to 9 clock pulses) must either check SDA or send
additional STOP conditions to ensure the bus has been released. Otherwise
random data will be written to a device!