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 :/.
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 */
--
js
suse labs
