Re: [PATCH v2] i2c: stub: Add support for SMBus block commands

From: Guenter Roeck
Date: Sun Jul 13 2014 - 11:46:56 EST

On 07/13/2014 08:13 AM, Jean Delvare wrote:
On Sun, 13 Jul 2014 08:04:54 -0700, Guenter Roeck wrote:
On 07/13/2014 12:21 AM, Jean Delvare wrote:
Hi Guenter,

On Sat, 12 Jul 2014 08:05:49 -0700, Guenter Roeck wrote:
Any idea how we could inject errors ? Error path testing would be quite useful.

Good idea. This should probably be done with a sysfs attribute so that
it can be turned on and off as desired. Off by default, of course. Some
other subsystems already support error injection, you could check how
they are doing it, do that we do not diverge needlessly.

Do you think there is any value in failing with different error codes,
or just -EIO is enough?

How about writing the error code to return into the attribute ?
Write anything negative, and it is returned as error. Write 0,
and the driver works as normal.

This is smart, I like it :)

Do you think it should fail all the time when error injection is
enabled, or is there a value in having only a certain % of commands

For my purposes I would want it to fail reliably. We could add some fanciness,
though: Provide a second attribute which specifies how many operations should
pass before the first failure.

Let's start simple and just implement what you need.

I would actually benefit from both. The ability to return an error unconditionally
lets me test the first error path. The ability to return an error starting with the
n-th transfer lets me test the n-th error path.


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