linux-kernel - Re: [PATCH 0/7] gpio: mockup: extensions for testing purposes

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Date:   Tue, 31 Jan 2017 15:05:41 +0100
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Alexandre Courbot <gnurou@...il.com>,
        Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/7] gpio: mockup: extensions for testing purposes

2017-01-31 14:28 GMT+01:00 Linus Walleij <linus.walleij@...aro.org>:
> On Wed, Jan 25, 2017 at 4:34 PM, Bartosz Golaszewski
> <bgolaszewski@...libre.com> wrote:
>
>> This series proposes to extend the gpio framework by allowing to
>> inject line events from the kernel code and by providing a debugfs
>> interface for that to the gpio-mockup driver. We also allow the
>> user to request that the mockup driver name the lines.
>
> I sympathize fully with the goal and intentions of the series, I
> agree: this is awesome to have for testing and validation of
> GPIO.
>
> I'm reluctant about the changes to gpiolib and want to make that
> code as optional as possible, definately #ifdef if nothing else
> works. Otherwise the memory footprint people will get me for this,
> haha. ;)
>
> The absolutely best would be if the driver could inject "real"
> irqs and also exercise the gpiolib irqchip helpers. I have been
> vaguely thinking that sofware interrupts should be able to do this
> but I'm not very versed in that kind of stuff.
>

This was my initial idea, but I thought it's not very likely that
Thomas Gleixner would allow me to allocate a new software interrupt
just for the sake of testing gpiolib. Also: the handling of softirqs
seems to be a bit different than regular IRQs, but I'm too not an
expert.

> The changes to gpio-mockup.c are entirely uncontroversial, it
> is for testing so I'm willing to accept almost anything if it looks
> maintainable and helps in testing.
>

How about creating a new config option GPIOLIB_LINE_EVENT_DEBUG that
would be selected by GPIO_MOCKUP and enclosing the relevant gpiolib
code with ifdefs (+ potentially comments explaining what's being done
and why)?

Thanks,
Bartosz