On Wed, 05 Oct 2022, Jiri Slaby <jirislaby@xxxxxxxxxx> wrote: > On 04. 10. 22, 12:52, Jani Nikula wrote: >> On Tue, 04 Oct 2022, "Jiri Slaby (SUSE)" <jirislaby@xxxxxxxxxx> wrote: >>> When DRM_I915=y and BACKLIGHT_CLASS_DEVICE=m, the build fails: >>> ld: drivers/gpu/drm/i915/display/intel_backlight.o: in function `intel_backlight_device_register': >>> intel_backlight.c:(.text+0x5587): undefined reference to `backlight_device_get_by_name' >>> >>> ld: drivers/gpu/drm/i915/display/intel_backlight.o: in function `intel_backlight_device_unregister': >>> intel_backlight.c:(.text+0x576e): undefined reference to `backlight_device_unregister' >>> >>> To fix this, use IS_REACHABLE(), not IS_ENABLED() in backlight. That is, >>> with the above config, backlight support is disabled. >> >> So I don't want this. I'll take a patch that fixes the dependencies to >> block DRM_I915=y and BACKLIGHT_CLASS_DEVICE=m. Nobody wants that combo, >> and IMO using IS_REACHABLE() is a workaround to hide a broken config >> under the carpet. >> >> The right thing to do is >> >> config DRM_I915 >> depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n. >> >> We're selecting BACKLIGHT_CLASS_DEVICE because almost everyone else is >> too, and a combo of selecting and depending leads to circular >> dependencies. But depending is the right fix. > > I'm not sure what should I do now. If I do: > --- a/drivers/gpu/drm/i915/Kconfig > +++ b/drivers/gpu/drm/i915/Kconfig > @@ -4,6 +4,7 @@ config DRM_I915 > depends on DRM > depends on X86 && PCI > depends on !PREEMPT_RT > + depends on (BACKLIGHT_CLASS_DEVICE && ACPI) || > (BACKLIGHT_CLASS_DEVICE=n && ACPI=n) > select INTEL_GTT if X86 > select INTERVAL_TREE > # we need shmfs for the swappable backing store, and in particular > @@ -21,7 +22,6 @@ config DRM_I915 > select IRQ_WORK > # i915 depends on ACPI_VIDEO when ACPI is enabled > # but for select to work, need to select ACPI_VIDEO's > dependencies, ick > - select BACKLIGHT_CLASS_DEVICE if ACPI > select INPUT if ACPI > select X86_PLATFORM_DEVICES if ACPI > select ACPI_WMI if ACPI > > I get: > drivers/gpu/drm/i915/Kconfig:2:error: recursive dependency detected! > drivers/gpu/drm/i915/Kconfig:2: symbol DRM_I915 depends on > BACKLIGHT_CLASS_DEVICE > drivers/video/backlight/Kconfig:143: symbol BACKLIGHT_CLASS_DEVICE is > selected by DRM_FSL_DCU > drivers/gpu/drm/fsl-dcu/Kconfig:2: symbol DRM_FSL_DCU depends on > COMMON_CLK > drivers/clk/Kconfig:21: symbol COMMON_CLK is selected by X86_INTEL_QUARK > arch/x86/Kconfig:633: symbol X86_INTEL_QUARK depends on > X86_PLATFORM_DEVICES > drivers/platform/x86/Kconfig:6: symbol X86_PLATFORM_DEVICES is selected > by DRM_I915 > > > Those dependencies are really cumbersome :/. Yes. They could be fixed, though [1]. IS_REACHABLE() is just band-aid. BR, Jani. [1] https://lore.kernel.org/r/1413580403-16225-1-git-send-email-jani.nikula@xxxxxxxxx > >> Documentation/kbuild/kconfig-language.rst: >> >> Note: >> select should be used with care. select will force >> a symbol to a value without visiting the dependencies. >> By abusing select you are able to select a symbol FOO even >> if FOO depends on BAR that is not set. >> In general use select only for non-visible symbols >> (no prompts anywhere) and for symbols with no dependencies. >> That will limit the usefulness but on the other hand avoid >> the illegal configurations all over. >> >> >> BR, >> Jani. >> >>> >>> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> >>> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> >>> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> >>> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> >>> Cc: David Airlie <airlied@xxxxxxxxx> >>> Cc: Daniel Vetter <daniel@xxxxxxxx> >>> Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx >>> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx >>> Reported-by: Martin Liška <mliska@xxxxxxx> >>> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@xxxxxxxxxx> >>> --- >>> drivers/gpu/drm/i915/display/intel_backlight.c | 2 +- >>> drivers/gpu/drm/i915/display/intel_backlight.h | 2 +- >>> 2 files changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu/drm/i915/display/intel_backlight.c >>> index beba39a38c87..c1ba68796b6d 100644 >>> --- a/drivers/gpu/drm/i915/display/intel_backlight.c >>> +++ b/drivers/gpu/drm/i915/display/intel_backlight.c >>> @@ -825,7 +825,7 @@ void intel_backlight_enable(const struct intel_crtc_state *crtc_state, >>> mutex_unlock(&dev_priv->display.backlight.lock); >>> } >>> >>> -#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) >>> +#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE) >>> static u32 intel_panel_get_backlight(struct intel_connector *connector) >>> { >>> struct drm_i915_private *dev_priv = to_i915(connector->base.dev); >>> diff --git a/drivers/gpu/drm/i915/display/intel_backlight.h b/drivers/gpu/drm/i915/display/intel_backlight.h >>> index 339643f63897..207fe1c613d8 100644 >>> --- a/drivers/gpu/drm/i915/display/intel_backlight.h >>> +++ b/drivers/gpu/drm/i915/display/intel_backlight.h >>> @@ -36,7 +36,7 @@ u32 intel_backlight_invert_pwm_level(struct intel_connector *connector, u32 leve >>> u32 intel_backlight_level_to_pwm(struct intel_connector *connector, u32 level); >>> u32 intel_backlight_level_from_pwm(struct intel_connector *connector, u32 val); >>> >>> -#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) >>> +#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE) >>> int intel_backlight_device_register(struct intel_connector *connector); >>> void intel_backlight_device_unregister(struct intel_connector *connector); >>> #else /* CONFIG_BACKLIGHT_CLASS_DEVICE */ >> -- Jani Nikula, Intel Open Source Graphics Center
