[PATCH v2 2/4] drm: Add drm_get_acpi_edid() helper

[Mario Limonciello]

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.

Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
---
v1->v2:
 * Split code from previous amdgpu specific helper to generic drm helper.
---
 drivers/gpu/drm/Kconfig    |  4 +++
 drivers/gpu/drm/drm_edid.c | 73 ++++++++++++++++++++++++++++++++++++++
 include/drm/drm_edid.h     |  1 +
 3 files changed, 78 insertions(+)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 2520db0b776e..0065dcb63745 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -21,6 +21,10 @@ 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 ACPI_WMI if 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);
-- 
2.34.1