From: Jani Nikula Date: Fri, 26 Sep 2025 11:10:32 +0000 (+0300) Subject: drm/{i915,xe}: driver agnostic drm to display pointer chase X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=97825e1c6de7315cba9acb6c1371f1a87dedd904;p=thirdparty%2Fkernel%2Flinux.git drm/{i915,xe}: driver agnostic drm to display pointer chase The display driver needs to get from the struct drm_device pointer to the struct intel_display pointer. Currently, this depends on knowledge of the struct drm_i915_private and struct xe_device definitions, but we'd like to hide those definitions from display. Require the struct drm_device and struct intel_display * members within struct drm_i915_private and struct xe_device to be placed next to each other, to be able to figure out the display pointer without knowledge of the structures. Use a generic dummy device structure to define the relative offsets of the drm and display members, and add static assertions to ensure this holds for both i915 and xe. Use the dummy structure to do the pointer chase from struct drm_device * to struct intel_display *. This requires moving the display member in struct xe_device after the drm member. Cc: Lucas De Marchi Cc: Rodrigo Vivi Cc: Ville Syrjala Suggested-by: Simona Vetter Reviewed-by: Lucas De Marchi Link: https://lore.kernel.org/r/20250926111032.1188876-1-jani.nikula@intel.com Signed-off-by: Jani Nikula --- diff --git a/drivers/gpu/drm/i915/display/intel_display_conversion.c b/drivers/gpu/drm/i915/display/intel_display_conversion.c index d56065f226554..9a47aa38cf824 100644 --- a/drivers/gpu/drm/i915/display/intel_display_conversion.c +++ b/drivers/gpu/drm/i915/display/intel_display_conversion.c @@ -1,15 +1,21 @@ // SPDX-License-Identifier: MIT /* Copyright © 2024 Intel Corporation */ -#include "i915_drv.h" -#include "intel_display_conversion.h" +#include -static struct intel_display *__i915_to_display(struct drm_i915_private *i915) -{ - return i915->display; -} +#include "intel_display_conversion.h" struct intel_display *__drm_to_display(struct drm_device *drm) { - return __i915_to_display(to_i915(drm)); + /* + * Note: This relies on both struct drm_i915_private and struct + * xe_device having the struct drm_device and struct intel_display * + * members at the same relative offsets, as defined by struct + * __intel_generic_device. + * + * See also INTEL_DISPLAY_MEMBER_STATIC_ASSERT(). + */ + struct __intel_generic_device *d = container_of(drm, struct __intel_generic_device, drm); + + return d->display; } diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c index 95165e45de745..b46cb54ef5dc3 100644 --- a/drivers/gpu/drm/i915/i915_driver.c +++ b/drivers/gpu/drm/i915/i915_driver.c @@ -46,6 +46,7 @@ #include #include #include +#include #include "display/i9xx_display_sr.h" #include "display/intel_bw.h" @@ -737,6 +738,9 @@ static void i915_welcome_messages(struct drm_i915_private *dev_priv) "DRM_I915_DEBUG_RUNTIME_PM enabled\n"); } +/* Ensure drm and display members are placed properly. */ +INTEL_DISPLAY_MEMBER_STATIC_ASSERT(struct drm_i915_private, drm, display); + static struct drm_i915_private * i915_driver_create(struct pci_dev *pdev, const struct pci_device_id *ent) { diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 03e497d2081e4..6e159bb8ad2fe 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -174,6 +174,7 @@ struct i915_selftest_stash { struct drm_i915_private { struct drm_device drm; + /* display device data, must be placed after drm device member */ struct intel_display *display; /* FIXME: Device release actions should all be moved to drmm_ */ diff --git a/drivers/gpu/drm/xe/display/xe_display.c b/drivers/gpu/drm/xe/display/xe_display.c index 19e691fccf8ce..5f4044e631852 100644 --- a/drivers/gpu/drm/xe/display/xe_display.c +++ b/drivers/gpu/drm/xe/display/xe_display.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include "soc/intel_dram.h" @@ -35,6 +36,9 @@ #include "skl_watermark.h" #include "xe_module.h" +/* Ensure drm and display members are placed properly. */ +INTEL_DISPLAY_MEMBER_STATIC_ASSERT(struct xe_device, drm, display); + /* Xe device functions */ /** diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h index a6c361db11d96..53264b2bb8324 100644 --- a/drivers/gpu/drm/xe/xe_device_types.h +++ b/drivers/gpu/drm/xe/xe_device_types.h @@ -217,6 +217,11 @@ struct xe_device { /** @drm: drm device */ struct drm_device drm; +#if IS_ENABLED(CONFIG_DRM_XE_DISPLAY) + /** @display: display device data, must be placed after drm device member */ + struct intel_display *display; +#endif + /** @devcoredump: device coredump */ struct xe_devcoredump devcoredump; @@ -617,8 +622,6 @@ struct xe_device { * drm_i915_private during build. After cleanup these should go away, * migrating to the right sub-structs */ - struct intel_display *display; - const struct dram_info *dram_info; /* diff --git a/include/drm/intel/display_member.h b/include/drm/intel/display_member.h new file mode 100644 index 0000000000000..0319ea560b602 --- /dev/null +++ b/include/drm/intel/display_member.h @@ -0,0 +1,42 @@ +/* SPDX-License-Identifier: MIT */ +/* Copyright © 2025 Intel Corporation */ + +#ifndef __DRM_INTEL_DISPLAY_H__ +#define __DRM_INTEL_DISPLAY_H__ + +#include +#include +#include + +#include + +struct intel_display; + +/* + * A dummy device struct to define the relative offsets of drm and display + * members. With the members identically placed in struct drm_i915_private and + * struct xe_device, this allows figuring out the struct intel_display pointer + * without the definition of either driver specific structure. + */ +struct __intel_generic_device { + struct drm_device drm; + struct intel_display *display; +}; + +/** + * INTEL_DISPLAY_MEMBER_STATIC_ASSERT() - ensure correct placing of drm and display members + * @type: The struct to check + * @drm_member: Name of the struct drm_device member + * @display_member: Name of the struct intel_display * member. + * + * Use this static assert macro to ensure the struct drm_i915_private and struct + * xe_device struct drm_device and struct intel_display * members are at the + * same relative offsets. + */ +#define INTEL_DISPLAY_MEMBER_STATIC_ASSERT(type, drm_member, display_member) \ + static_assert( \ + offsetof(struct __intel_generic_device, display) - offsetof(struct __intel_generic_device, drm) == \ + offsetof(type, display_member) - offsetof(type, drm_member), \ + __stringify(type) " " __stringify(drm_member) " and " __stringify(display_member) " members at invalid offsets") + +#endif