Re: [PATCH v3 2/5] drm: Add drm_get_acpi_edid() helper

[Mario Limonciello <mario.limonciello@amd.com>]

On 2/2/2024 04:29, Jani Nikula wrote:
> On Thu, 01 Feb 2024, Mario Limonciello <mario.limonciello@amd.com> wrote:
>> Some manufacturers have intentionally put an EDID that differs from
>> the EDID on the internal panel on laptops.  Drivers can call this
>> helper to attempt to fetch the EDID from the BIOS's ACPI _DDC method.
> 
> I'm really not happy about adding new struct edid based APIs to
> drm_edid.[ch]. Everything new should be struct drm_edid based. All
> drivers should be converting towards struct drm_edid, instead of adding
> more legacy to rip out later.

OK; I'll redo it with struct drm_edid.

The changeover for amdgpu to use drm_edid is going to be a pretty 
involved effort so I'm going to use a get_raw in amdgpu for now so we 
can unblock the issue this is fixing and let that part get removed when 
the rest of the overhaul gets done there.

> 
> BR,
> Jani.
> 
>>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>> v1->v2:
>>   * Split code from previous amdgpu specific helper to generic drm helper.
>> v2->v3:
>>   * Add an extra select to fix a variety of randconfig errors found from
>>     LKP robot.
>> ---
>>   drivers/gpu/drm/Kconfig    |  5 +++
>>   drivers/gpu/drm/drm_edid.c | 73 ++++++++++++++++++++++++++++++++++++++
>>   include/drm/drm_edid.h     |  1 +
>>   3 files changed, 79 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>> index 2520db0b776e..14df907c96c8 100644
>> --- a/drivers/gpu/drm/Kconfig
>> +++ b/drivers/gpu/drm/Kconfig
>> @@ -21,6 +21,11 @@ menuconfig DRM
>>   	select KCMP
>>   	select VIDEO_CMDLINE
>>   	select VIDEO_NOMODESET
>> +	select ACPI_VIDEO if ACPI
>> +	select BACKLIGHT_CLASS_DEVICE if ACPI
>> +	select INPUT if ACPI
>> +	select X86_PLATFORM_DEVICES if ACPI && X86
>> +	select ACPI_WMI if ACPI && X86
>>   	help
>>   	  Kernel-level support for the Direct Rendering Infrastructure (DRI)
>>   	  introduced in XFree86 4.0. If you say Y here, you need to select
>> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
>> index 69c68804023f..1fbbeaa664b2 100644
>> --- a/drivers/gpu/drm/drm_edid.c
>> +++ b/drivers/gpu/drm/drm_edid.c
>> @@ -28,6 +28,7 @@
>>    * DEALINGS IN THE SOFTWARE.
>>    */
>>   
>> +#include <acpi/video.h>
>>   #include <linux/bitfield.h>
>>   #include <linux/cec.h>
>>   #include <linux/hdmi.h>
>> @@ -2188,6 +2189,47 @@ drm_do_probe_ddc_edid(void *data, u8 *buf, unsigned int block, size_t len)
>>   	return ret == xfers ? 0 : -1;
>>   }
>>   
>> +/**
>> + * drm_do_probe_acpi_edid() - get EDID information via ACPI _DDC
>> + * @data: struct drm_device
>> + * @buf: EDID data buffer to be filled
>> + * @block: 128 byte EDID block to start fetching from
>> + * @len: EDID data buffer length to fetch
>> + *
>> + * Try to fetch EDID information by calling acpi_video_get_edid() function.
>> + *
>> + * Return: 0 on success or error code on failure.
>> + */
>> +static int
>> +drm_do_probe_acpi_edid(void *data, u8 *buf, unsigned int block, size_t len)
>> +{
>> +	struct drm_device *ddev = data;
>> +	struct acpi_device *acpidev = ACPI_COMPANION(ddev->dev);
>> +	unsigned char start = block * EDID_LENGTH;
>> +	void *edid;
>> +	int r;
>> +
>> +	if (!acpidev)
>> +		return -ENODEV;
>> +
>> +	/* fetch the entire edid from BIOS */
>> +	r = acpi_video_get_edid(acpidev, ACPI_VIDEO_DISPLAY_LCD, -1, &edid);
>> +	if (r < 0) {
>> +		DRM_DEBUG_KMS("Failed to get EDID from ACPI: %d\n", r);
>> +		return -EINVAL;
>> +	}
>> +	if (len > r || start > r || start + len > r) {
>> +		r = EINVAL;
>> +		goto cleanup;
>> +	}
>> +
>> +	memcpy(buf, edid + start, len);
>> +	r = 0;
>> +cleanup:
>> +	kfree(edid);
>> +	return r;
>> +}
>> +
>>   static void connector_bad_edid(struct drm_connector *connector,
>>   			       const struct edid *edid, int num_blocks)
>>   {
>> @@ -2643,6 +2685,37 @@ struct edid *drm_get_edid(struct drm_connector *connector,
>>   }
>>   EXPORT_SYMBOL(drm_get_edid);
>>   
>> +/**
>> + * drm_get_acpi_edid - get EDID data, if available
>> + * @connector: connector we're probing
>> + *
>> + * Use the BIOS to attempt to grab EDID data if possible.  If found,
>> + * attach it to the connector.
>> + *
>> + * Return: Pointer to valid EDID or NULL if we couldn't find any.
>> + */
>> +struct edid *drm_get_acpi_edid(struct drm_connector *connector)
>> +{
>> +	struct edid *edid = NULL;
>> +
>> +	switch (connector->connector_type) {
>> +	case DRM_MODE_CONNECTOR_LVDS:
>> +	case DRM_MODE_CONNECTOR_eDP:
>> +		break;
>> +	default:
>> +		return NULL;
>> +	}
>> +
>> +	if (connector->force == DRM_FORCE_OFF)
>> +		return NULL;
>> +
>> +	edid = _drm_do_get_edid(connector, drm_do_probe_acpi_edid, connector->dev, NULL);
>> +
>> +	drm_connector_update_edid_property(connector, edid);
>> +	return edid;
>> +}
>> +EXPORT_SYMBOL(drm_get_acpi_edid);
>> +
>>   /**
>>    * drm_edid_read_custom - Read EDID data using given EDID block read function
>>    * @connector: Connector to use
>> diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
>> index 518d1b8106c7..60fbdc06badc 100644
>> --- a/include/drm/drm_edid.h
>> +++ b/include/drm/drm_edid.h
>> @@ -412,6 +412,7 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,
>>   	void *data);
>>   struct edid *drm_get_edid(struct drm_connector *connector,
>>   			  struct i2c_adapter *adapter);
>> +struct edid *drm_get_acpi_edid(struct drm_connector *connector);
>>   u32 drm_edid_get_panel_id(struct i2c_adapter *adapter);
>>   struct edid *drm_get_edid_switcheroo(struct drm_connector *connector,
>>   				     struct i2c_adapter *adapter);
>