linux-kernel - Re: [PATCH] drm/nouveau: fix LEDS

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Message-ID: <CAKb7UviRQ5_7nAeQ1zfacsiM1f13gohHRHeDZaD+ZOXM8srFKw@mail.gmail.com>
Date:   Tue, 8 Nov 2016 10:46:07 -0500
From:   Ilia Mirkin <imirkin@...m.mit.edu>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Ben Skeggs <bskeggs@...hat.com>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/nouveau: fix LEDS_CLASS=m configuration

On Tue, Nov 8, 2016 at 8:56 AM, Arnd Bergmann <arnd@...db.de> wrote:
> The newly introduced LED handling for nouveau fails to link when the
> driver is built-in but the LED subsystem is a loadable module:
>
> drivers/gpu/drm/nouveau/nouveau.o: In function `nouveau_do_suspend':
> tvnv17.c:(.text.nouveau_do_suspend+0x10): undefined reference to `nouveau_led_suspend'
> drivers/gpu/drm/nouveau/nouveau.o: In function `nouveau_do_resume':
> tvnv17.c:(.text.nouveau_do_resume+0xf0): undefined reference to `nouveau_led_resume'
> drivers/gpu/drm/nouveau/nouveau.o: In function `nouveau_drm_unload':
> tvnv17.c:(.text.nouveau_drm_unload+0x34): undefined reference to `nouveau_led_fini'
> drivers/gpu/drm/nouveau/nouveau.o: In function `nouveau_drm_load':
> tvnv17.c:(.text.nouveau_drm_load+0x7d0): undefined reference to `nouveau_led_init'
>
> This adds a separate Kconfig symbol for the LED support that
> correctly tracks the dependencies.
>
> Fixes: 8d021d71b324 ("drm/nouveau/drm/nouveau: add a LED driver for the NVIDIA logo")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/gpu/drm/nouveau/Kbuild        | 2 +-
>  drivers/gpu/drm/nouveau/Kconfig       | 8 ++++++++
>  drivers/gpu/drm/nouveau/nouveau_led.h | 2 +-
>  3 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/Kbuild b/drivers/gpu/drm/nouveau/Kbuild
> index fde6e3656636..5e00e911daa6 100644
> --- a/drivers/gpu/drm/nouveau/Kbuild
> +++ b/drivers/gpu/drm/nouveau/Kbuild
> @@ -22,7 +22,7 @@ nouveau-$(CONFIG_DEBUG_FS) += nouveau_debugfs.o
>  nouveau-y += nouveau_drm.o
>  nouveau-y += nouveau_hwmon.o
>  nouveau-$(CONFIG_COMPAT) += nouveau_ioc32.o
> -nouveau-$(CONFIG_LEDS_CLASS) += nouveau_led.o
> +nouveau-$(CONFIG_DRM_NOUVEAU_LED) += nouveau_led.o
>  nouveau-y += nouveau_nvif.o
>  nouveau-$(CONFIG_NOUVEAU_PLATFORM_DRIVER) += nouveau_platform.o
>  nouveau-y += nouveau_usif.o # userspace <-> nvif
> diff --git a/drivers/gpu/drm/nouveau/Kconfig b/drivers/gpu/drm/nouveau/Kconfig
> index 78631fb61adf..715cd6f4dc31 100644
> --- a/drivers/gpu/drm/nouveau/Kconfig
> +++ b/drivers/gpu/drm/nouveau/Kconfig
> @@ -46,6 +46,14 @@ config NOUVEAU_DEBUG
>           The paranoia and spam levels will add a lot of extra checks which
>           may potentially slow down driver operation.
>
> +config DRM_NOUVEAU_LED
> +       bool "Support for logo LED"
> +       depends on DRM_NOUVEAU && LEDS_CLASS
> +       depends on !(DRM_NOUVEAU=y && LEDS_CLASS=m)
> +       help
> +         Say Y here to enabling controlling the brightness of the
> +         LED behind NVIDIA logo on certain Titan cards.

This is a very odd restriction... could this be written as

depends on DRM_NOUVEAU
select LEDS_CLASS

Or will that not flip the LEDS_CLASS from m to y in case
DRM_NOUVEAU=y? If not, is there a way to cause that to happen?

Separately, perhaps we should just drop this LEDS_CLASS select into
DRM_NOUVEAU? We've tended to avoid adding tons of options.

Cheers,

  -ilia