On 8/22/2024 01:12, Thomas Weißschuh wrote:
> On 2024-08-21 15:51:17+0000, Mario Limonciello wrote:
>> On 8/18/2024 01:56, Thomas Weißschuh wrote:
>>> Panels using a PWM-controlled backlight source 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 minimum valid backlight value
>>> can be maintained as part of the kernel.
>>>
>>> Signed-off-by: Thomas Weißschuh <linux at weissschuh.net>
>>> Tested-by: Dustin L. Howett <dustin at howett.net>
>>
>> One small nit below but otherwise this patch is fine to me.
>>
>> Reviewed-by: Mario Limonciello <mario.limonciello at amd.com>
>>
>>> ---
>>> 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 | 70 ++++++++++++++++++++++++++++
>>> include/drm/drm_utils.h | 4 ++
>>> 5 files changed, 82 insertions(+)
>>>
>>> diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst
>>> index 8435e8621cc0..a26989500129 100644
>>> --- a/Documentation/gpu/drm-kms-helpers.rst
>>> +++ b/Documentation/gpu/drm-kms-helpers.rst
>>> @@ -230,6 +230,9 @@ 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 6b2c6b91f962..9ebb8cdb535e 100644
>>> --- a/drivers/gpu/drm/Kconfig
>>> +++ b/drivers/gpu/drm/Kconfig
>>> @@ -454,6 +454,10 @@ config DRM_HYPERV
>>> config DRM_EXPORT_FOR_TESTS
>>> bool
>>> +# 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 68cc9258ffc4..adf85999aee2 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..6b8bbed77c7f
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/drm_panel_backlight_quirks.c
>>> @@ -0,0 +1,70 @@
>>> +// 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_edid.h>
>>> +#include <drm/drm_utils.h>
>>> +
>>> +struct drm_panel_min_backlight_quirk {
>>> + struct {
>>> + enum dmi_field field;
>>> + const char * const value;
>>> + } dmi_match;
>>> + struct drm_edid_ident ident;
>>> + u8 min_brightness;
>>> +};
>>> +
>>> +static const struct drm_panel_min_backlight_quirk drm_panel_min_backlight_quirks[] = {
>>> +};
>>> +
>>> +static bool drm_panel_min_backlight_quirk_matches(const struct drm_panel_min_backlight_quirk *quirk,
>>> + const struct drm_edid *edid)
>>> +{
>>> + if (!dmi_match(quirk->dmi_match.field, quirk->dmi_match.value))
>>> + return false;
>>> +
>>> + if (!drm_edid_match(edid, &quirk->ident))
>>> + return false;
>>> +
>>> + return true;
>>> +}
>>> +
>>> +/**
>>> + * drm_get_panel_min_brightness_quirk - Get minimum supported brightness level for a panel.
>>> + * @edid: EDID of the panel to check
>>> + *
>>> + * This function checks for platform specific (e.g. DMI based) quirks
>>> + * providing info on the minimum backlight brightness for systems where this
>>> + * cannot be probed correctly from the hard-/firm-ware.
>>> + *
>>> + * Returns:
>>> + * A negative error value or
>>> + * an override value in the range [0, 255] representing 0-100% to be scaled to
>>> + * the drivers target range.
>>> + */
>>> +int drm_get_panel_min_brightness_quirk(const struct drm_edid *edid)
>>> +{
>>> + const struct drm_panel_min_backlight_quirk *quirk;
>>> + size_t i;
>>
>> Nit: this doesn't really seem like it needs to be size_t. Shouldn't it just
>> be an unsigned int?
>
> ARRAY_SIZE() works with sizeof() which returns size_t.
> It doesn't really matter, but I slightly prefer to keep the size_t.
Ah thanks, I didn't realize that. Feel free to leave as is then.
>
>>> +
>>> + if (!IS_ENABLED(CONFIG_DMI))
>>> + return -ENODATA;
>>> +
>>> + if (!edid)
>>> + return -EINVAL;
>>> +
>>> + for (i = 0; i < ARRAY_SIZE(drm_panel_min_backlight_quirks); i++) {
>>> + quirk = &drm_panel_min_backlight_quirks[i];
>>> +
>>> + if (drm_panel_min_backlight_quirk_matches(quirk, edid))
>>> + return quirk->min_brightness;
>>> + }
>>> +
>>> + return -ENODATA;
>>> +}
>>> +EXPORT_SYMBOL(drm_get_panel_min_brightness_quirk);
>>> +
>>> +MODULE_DESCRIPTION("Quirks for panel backlight overrides");
>>> +MODULE_LICENSE("GPL");
>>> diff --git a/include/drm/drm_utils.h b/include/drm/drm_utils.h
>>> index 70775748d243..15fa9b6865f4 100644
>>> --- a/include/drm/drm_utils.h
>>> +++ b/include/drm/drm_utils.h
>>> @@ -12,8 +12,12 @@
>>> #include <linux/types.h>
>>> +struct drm_edid;
>>> +
>>> int drm_get_panel_orientation_quirk(int width, int height);
>>> +int drm_get_panel_min_brightness_quirk(const struct drm_edid *edid);
>>> +
>>> signed long drm_timeout_abs_to_jiffies(int64_t timeout_nsec);
>>> #endif
>>>
>>