From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH v2] i2c: stub: Add support for SMBus block commands Date: Sun, 13 Jul 2014 08:46:41 -0700 Message-ID: <53C2A9E1.2080807@roeck-us.net> References: <1404742983-27303-1-git-send-email-linux@roeck-us.net> <20140708215453.0677d3ed@endymion.delvare> <53BC4F15.9030608@roeck-us.net> <20140712112019.618d8a03@endymion.delvare> <53C14ECD.7050105@roeck-us.net> <20140713092127.4bedfa18@endymion.delvare> <53C2A016.2070906@roeck-us.net> <20140713171343.0a4ba58d@endymion.delvare> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140713171343.0a4ba58d-R0o5gVi9kd7kN2dkZ6Wm7A@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jean Delvare Cc: Wolfram Sang , Randy Dunlap , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-i2c@vger.kernel.org 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 >>> fail? >> >> 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. Guenter