drm/i915: use fine grained -Woverride-init disable

Use localized __diag_push(), __diag_ignore_all() with rationale, and
__diag_pop() for specific initializations instead of blanket disabling
of -Woverride-init across several files.

Note that we've tried this before with commit 88e9664434c9 ("drm/i915:
use localized __diag_ignore_all() instead of per file") and reverted in
commit 290d16104575 ("Revert "drm/i915: use localized
__diag_ignore_all() instead of per file""). The issue turned out to be
in __diag_ignore_all() and it was fixed by commit 689b097a06ba
("compiler-gcc: Suppress -Wmissing-prototypes warning for all supported
GCC"). So we should be able to pull this off now.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240328102455.944131-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/Makefile

@@ -32,11 +32,6 @@ endif
 # Enable -Werror in CI and development
 subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
 
-# Fine grained warnings disable
-CFLAGS_i915_pci.o = $(call cc-disable-warning, override-init)
-CFLAGS_display/intel_display_device.o = $(call cc-disable-warning, override-init)
-CFLAGS_display/intel_fbdev.o = $(call cc-disable-warning, override-init)
-
 # Support compiling the display code separately for both i915 and xe
 # drivers. Define I915 when building i915.
 subdir-ccflags-y += -DI915

drivers/gpu/drm/i915/display/intel_display_device.c

@@ -17,6 +17,9 @@
 #include "intel_display_reg_defs.h"
 #include "intel_fbc.h"
 
+__diag_push();
+__diag_ignore_all("-Woverride-init", "Allow field initialization overrides for display info");
+
 static const struct intel_display_device_info no_display = {};
 
 #define PIPE_A_OFFSET		0x70000
@@ -768,6 +771,8 @@ static const struct intel_display_device_info xe2_lpd_display = {
 		BIT(INTEL_FBC_C) | BIT(INTEL_FBC_D),
 };
 
+__diag_pop();
+
 /*
  * Separate detection for no display cases to keep the display id array simple.
  *

drivers/gpu/drm/i915/display/intel_fbdev.c

@@ -135,6 +135,9 @@ static int intel_fbdev_mmap(struct fb_info *info, struct vm_area_struct *vma)
 	return i915_gem_fb_mmap(obj, vma);
 }
 
+__diag_push();
+__diag_ignore_all("-Woverride-init", "Allow field initialization overrides for fb ops");
+
 static const struct fb_ops intelfb_ops = {
 	.owner = THIS_MODULE,
 	__FB_DEFAULT_DEFERRED_OPS_RDWR(intel_fbdev),
@@ -146,6 +149,8 @@ static const struct fb_ops intelfb_ops = {
 	.fb_mmap = intel_fbdev_mmap,
 };
 
+__diag_pop();
+
 static int intelfb_create(struct drm_fb_helper *helper,
 			  struct drm_fb_helper_surface_size *sizes)
 {

drivers/gpu/drm/i915/i915_pci.c

@@ -38,6 +38,9 @@
 #include "i915_reg.h"
 #include "intel_pci_config.h"
 
+__diag_push();
+__diag_ignore_all("-Woverride-init", "Allow field initialization overrides for device info");
+
 #define PLATFORM(x) .platform = (x)
 #define GEN(x) \
 	.__runtime.graphics.ip.ver = (x), \
@@ -785,6 +788,8 @@ static const struct intel_device_info mtl_info = {
 
 #undef PLATFORM
 
+__diag_pop();
+
 /*
  * Make sure any device matches here are from most specific to most
  * general.  For example, since the Quanta match is based on the subsystem

drivers/gpu/drm/xe/Makefile

@@ -169,9 +169,6 @@ subdir-ccflags-$(CONFIG_DRM_XE_DISPLAY) += \
 	-Ddrm_i915_gem_object=xe_bo \
 	-Ddrm_i915_private=xe_device
 
-CFLAGS_i915-display/intel_fbdev.o = $(call cc-disable-warning, override-init)
-CFLAGS_i915-display/intel_display_device.o = $(call cc-disable-warning, override-init)
-
 # Rule to build SOC code shared with i915
 $(obj)/i915-soc/%.o: $(srctree)/drivers/gpu/drm/i915/soc/%.c FORCE
 	$(call cmd,force_checksrc)