Panels using a PWM-controlled backlight source without an do not have a
standard way to communicate their valid PWM ranges.
On x86 the ranges are read from ACPI through driver-specific tables.
The built-in ranges are not necessarily correct, or may grow stale if an
older device can be retrofitted with newer panels.
Add a quirk infrastructure with which the valid backlight ranges can be
maintained as part of the kernel.
Signed-off-by: Thomas Weißschuh <li...@weissschuh.net>
---
Documentation/gpu/drm-kms-helpers.rst | 3 ++
drivers/gpu/drm/Kconfig | 4 ++
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/drm_panel_backlight_quirks.c | 67 ++++++++++++++++++++++++++++
include/drm/drm_utils.h | 11 +++++
5 files changed, 86 insertions(+)
diff --git a/Documentation/gpu/drm-kms-helpers.rst
b/Documentation/gpu/drm-kms-helpers.rst
index 59cfe8a7a8ba..1998a2675210 100644
--- a/Documentation/gpu/drm-kms-helpers.rst
+++ b/Documentation/gpu/drm-kms-helpers.rst
@@ -224,6 +224,9 @@ Panel Helper Reference
.. kernel-doc:: drivers/gpu/drm/drm_panel_orientation_quirks.c
:export:
+.. kernel-doc:: drivers/gpu/drm/drm_panel_backlight_quirks.c
+ :export:
+
Panel Self Refresh Helper Reference
===================================
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 959b19a04101..50ccb43315bf 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -443,6 +443,10 @@ config DRM_EXPORT_FOR_TESTS
config DRM_PANEL_ORIENTATION_QUIRKS
tristate
+# Separate option as not all DRM drivers use it
+config DRM_PANEL_BACKLIGHT_QUIRKS
+ tristate
+
config DRM_LIB_RANDOM
bool
default n
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index f9ca4f8fa6c5..6669913b907e 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -92,6 +92,7 @@ drm-$(CONFIG_DRM_PANIC) += drm_panic.o
obj-$(CONFIG_DRM) += drm.o
obj-$(CONFIG_DRM_PANEL_ORIENTATION_QUIRKS) += drm_panel_orientation_quirks.o
+obj-$(CONFIG_DRM_PANEL_BACKLIGHT_QUIRKS) += drm_panel_backlight_quirks.o
#
# Memory-management helpers
diff --git a/drivers/gpu/drm/drm_panel_backlight_quirks.c
b/drivers/gpu/drm/drm_panel_backlight_quirks.c
new file mode 100644
index 000000000000..a89b5fd1940e
--- /dev/null
+++ b/drivers/gpu/drm/drm_panel_backlight_quirks.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/array_size.h>
+#include <linux/dmi.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <drm/drm_connector.h>
+#include <drm/drm_utils.h>
+
+struct drm_panel_backlight_entry {
+ struct {
+ enum dmi_field field;
+ const char * const value;
+ } dmi_match;
+ struct drm_edid_ident ident;
+ struct drm_panel_backlight_quirk quirk;
+};
+
+static const struct drm_panel_backlight_entry drm_panel_backlight_entries[] = {
+};
+
+static bool drm_panel_backlight_entry_matches(const struct
drm_panel_backlight_entry *entry,
+ const struct drm_edid *edid)
+{
+ if (!dmi_match(entry->dmi_match.field, entry->dmi_match.value))
+ return false;
+
+ if (!drm_edid_match(edid, &entry->ident))
+ return false;
+
+ return true;
+}
+
+/**
+ * drm_get_panel_panel_quirk - Check for panel backlight quirks
+ * @edid: EDID of the panel to check
+ *
+ * This function checks for platform specific (e.g. DMI based) quirks
+ * providing info on backlight control for systems where this cannot be
+ * probed from the hard-/firm-ware.
+ *
+ * Returns:
+ * A struct drm_panel_backlight_quirk if a quirk is found or NULL otherwise.
+ */
+const struct drm_panel_backlight_quirk *drm_get_panel_backlight_quirk(const
struct drm_edid *edid)
+{
+ const struct drm_panel_backlight_entry *entry;
+ size_t i;
+
+ if (!IS_ENABLED(CONFIG_DMI))
+ return NULL;
+
+ if (!edid)
+ return NULL;
+
+ for (i = 0; i < ARRAY_SIZE(drm_panel_backlight_entries); i++) {
+ entry = &drm_panel_backlight_entries[i];
+
+ if (drm_panel_backlight_entry_matches(entry, edid))
+ return &entry->quirk;
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL(drm_get_panel_backlight_quirk);
+
+MODULE_LICENSE("GPL");
diff --git a/include/drm/drm_utils.h b/include/drm/drm_utils.h
index 70775748d243..37cc6de1a01a 100644
--- a/include/drm/drm_utils.h
+++ b/include/drm/drm_utils.h
@@ -11,9 +11,20 @@
#define __DRM_UTILS_H__
#include <linux/types.h>
+#include <drm/drm_edid.h>
+
+struct drm_panel_backlight_quirk {
+ struct {
+ bool pwm_min_brightness:1;
+ } overrides;
+
+ u8 pwm_min_brightness; /* min_brightness/255 of max */
+};
int drm_get_panel_orientation_quirk(int width, int height);
+const struct drm_panel_backlight_quirk *drm_get_panel_backlight_quirk(const
struct drm_edid *edid);
+
signed long drm_timeout_abs_to_jiffies(int64_t timeout_nsec);
#endif
--
2.45.2
