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

[Mario Limonciello <mario.limonciello@xxxxxxx>]

On 2/2/2024 04:29, Jani Nikula wrote:
> On Thu, 01 Feb 2024, Mario Limonciello <mario.limonciello@xxxxxxx> 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@xxxxxxx>
> > ---
> > 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);