linux-kernel - Re: [PATCH] gpio: tegra: don't auto-enable for COMPILE

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Date:	Wed, 20 Jul 2016 13:07:17 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Alexander Stein <alexanders83@....de>,
	William Breathitt Gray <vilhelm.gray@...il.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: tegra: don't auto-enable for COMPILE_TEST

On Wednesday, July 20, 2016 12:41:48 PM CEST Ingo Molnar wrote:
> * Linus Walleij <linus.walleij@...aro.org> wrote:
> 
> > On Wed, Jul 6, 2016 at 2:54 PM, Arnd Bergmann <arnd@...db.de> wrote:
> > 
> > > I stumbled over a build error with COMPILE_TEST and CONFIG_OF
> > > disabled:
> > >
> > > drivers/gpio/gpio-tegra.c: In function 'tegra_gpio_probe':
> > > drivers/gpio/gpio-tegra.c:603:9: error: 'struct gpio_chip' has no member named 'of_node'
> > >
> > > The problem is that the newly added GPIO_TEGRA Kconfig symbol
> > > does not have a dependency on CONFIG_OF. However, there is another
> > > problem here as the driver gets enabled unconditionally whenever
> > > COMPILE_TEST is set.
> > >
> > > This fixes both problems, by making the symbol user-visible
> > > when COMPILE_TEST is set and default-enabled for ARCH_TEGRA=y.
> > >
> > > As a side-effect, it is now possible to compile-test a Tegra
> > > kernel with GPIO support disabled, which is harmless.
> > >
> > > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > > Fixes: 4dd4dd1d2120 ("gpio: tegra: Allow compile test")
> > 
> > Patch applied.
> 
> This is still not upstream and this build failure is very prominent in the 
> upstream kernel right now.

Note that Linus Walleij is currently on vacation. I don't know
if Alexandre could forward this patch in the meantime.

I also have another patch for a similar regression in linux-next
that prevents an x86 allmodconfig kernel with CONFIG_OF=n
from building (see "pinctrl: bcm: add OF dependencies") and that
one hasn't made it into -next yet (unlike this one that is
fixed in -next but broken in v4.7).

> > I'm starting to get a bit tired about anything related to compile testing.
> 
> They are very useful in finding real problems as well, and some people
> (like me!  rely on being able to generate random kernel images and
>  boot them.

Agreed, I send many patches for build-time regressions every week. Most
of them are for harmless problems, but the other ones that find actual
bugs make it absolutely worthwhile.

I don't mind doing this, and most folks are happy to get an early
feedback about when things break. What's annoying is when I send
a patch within hours after a linux-next release that breaks something
and then the bug makes it into mainline anyway, weeks later.

	Arnd