linux-kernel - Re: [PATCH] drm/etnaviv: add thermal dependency

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Date:   Mon, 24 Apr 2017 19:39:27 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Lucas Stach <l.stach@...gutronix.de>
Cc:     David Airlie <airlied@...ux.ie>, Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        linux-pm@...r.kernel.org, Sujith Thomas <sujith.thomas@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Russell King <linux+etnaviv@...linux.org.uk>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        etnaviv@...ts.freedesktop.org,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH] drm/etnaviv: add thermal dependency

On Mon, Apr 24, 2017 at 12:44 PM, Lucas Stach <l.stach@...gutronix.de> wrote:
> Am Mittwoch, den 19.04.2017, 20:11 +0200 schrieb Arnd Bergmann:
>> When CONFIG_THERMAL is enabled as a loadable module, and etnaviv is
>> built-in, we get a link error:
>>
>> drivers/gpu/drm/etnaviv/etnaviv_gpu.o: In function `etnaviv_gpu_bind':
>> etnaviv_gpu.c:(.text.etnaviv_gpu_bind+0x34): undefined reference to `thermal_of_cooling_device_register'
>> etnaviv_gpu.c:(.text.etnaviv_gpu_bind+0xe0): undefined reference to `thermal_cooling_device_unregister'
>> drivers/gpu/drm/etnaviv/etnaviv_gpu.o: In function `etnaviv_gpu_unbind':
>> etnaviv_gpu.c:(.text.etnaviv_gpu_unbind+0xf0): undefined reference to `thermal_cooling_device_unregister'
>>
>> This adds a Kconfig dependency to prevent etnaviv from being built-in
>> with CONFIG_THERMAL=m, while still allowing the valid configurations.
>> Unfortunately, simply adding the dependency here breaks Kconfig through
>> a dependency loop involving lots of symbols all the way until ACPI_VIDEO,
>> which is the only video driver that explicitly selects 'THERMAL'. Turning
>> this into a 'depends on' addresses the problem.
>> For completeness, I'm also removing the redundant 'select THERMAL'
>> from INTEL_MENLOW, so no other driver uses that statement.
>>
>> Fixes: bcdfb5e56dc5 ("drm/etnaviv: add etnaviv cooling device")
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
> This patch mixes a few things, so the subject doesn't really fit. I'm
> fine with taking the patch trough my tree, if I can get an ACK on the
> ACPI part.

Actually the ACPI part triggered a new warning that I haven't figured
out completely yet. Please disregard my patch for the moment.

I think we can just drop the dependency in ACPI_VIDEO, but I'm not
entirely sure yet if we could hit a broken configuration with THERMAL=m
and ACPI_VIDEO=y in that case. Unfortunately we cannot use the
same trick in ACPI_VIDEO that I used for ETNAVIV, because of
another circular dependency in ACPI.

        Arnd