Re: [PATCH] drm/amd/display: Guard ACPI calls with CONFIG_ACPI

[Mario Limonciello]

On 6/10/2024 09:55, sunpeng...@amd.com wrote:
From: Leo Li <sunpeng...@amd.com>
To fix CONFIG_ACPI disabled build error.

Fixes: ec6f30c776ad ("drm/amd/display: Set default brightness according to 
ACPI")
Signed-off-by: Leo Li <sunpeng...@amd.com>
---
  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index a2c098f1b07c..6b3634db4c15 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4572,7 +4572,9 @@ amdgpu_dm_register_backlight_device(struct 
amdgpu_dm_connector *aconnector)
        struct drm_device *drm = aconnector->base.dev;
        struct amdgpu_display_manager *dm = &drm_to_adev(drm)->dm;
        struct backlight_properties props = { 0 };
+#if defined(CONFIG_ACPI)
        struct amdgpu_dm_backlight_caps caps = { 0 };
+#endif
        char bl_name[16];
  
  	if (aconnector->bl_idx == -1)
@@ -4585,6 +4587,7 @@ amdgpu_dm_register_backlight_device(struct 
amdgpu_dm_connector *aconnector)
                return;
        }
  
+#if defined(CONFIG_ACPI)
        amdgpu_acpi_get_backlight_caps(&caps);
        if (caps.caps_valid) {
                if (power_supply_is_system_supplied() > 0)
@@ -4593,6 +4596,9 @@ amdgpu_dm_register_backlight_device(struct 
amdgpu_dm_connector *aconnector)
                        props.brightness = caps.dc_level;
        } else
                props.brightness = AMDGPU_MAX_BL_LEVEL;
+#else
+       props.brightness = AMDGPU_MAX_BL_LEVEL;
+#endif

Hey Leo,

Thanks for the patch!

As caps is initialized to {0} caps.caps_valid will be invalid.  So I see 
two other ways to solve this that are a little cleaner (IMO):

1)  Just block the one call:

#if defined(CONFIG_ACPI)
        amdgpu_acpi_get_backlight_caps(&caps);
#endif

2) Add a stub inline no-op function for amdgpu_acpi_get_backlight_caps() 
to the header.

I personally think #2 is cleaner (less ifdef makes a lot more readable 
code).

  
  	props.max_brightness = AMDGPU_MAX_BL_LEVEL;
        props.type = BACKLIGHT_RAW;