drm/edid: add drm_edid_read_switcheroo()

Add a switcheroo variant to the struct drm_edid based EDID read
functions.

Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/4ab5ec994670ea50f95c8079c1f1ae915940b00f.1685437501.git.jani.nikula@intel.com

Author: jnikula

drivers/gpu/drm/drm_edid.c

@@ -2844,6 +2844,35 @@ struct edid *drm_get_edid_switcheroo(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_get_edid_switcheroo);
 
+/**
+ * drm_edid_read_switcheroo - get EDID data for a vga_switcheroo output
+ * @connector: connector we're probing
+ * @adapter: I2C adapter to use for DDC
+ *
+ * Wrapper around drm_edid_read_ddc() for laptops with dual GPUs using one set
+ * of outputs. The wrapper adds the requisite vga_switcheroo calls to
+ * temporarily switch DDC to the GPU which is retrieving EDID.
+ *
+ * Return: Pointer to valid EDID or %NULL if we couldn't find any.
+ */
+const struct drm_edid *drm_edid_read_switcheroo(struct drm_connector *connector,
+						struct i2c_adapter *adapter)
+{
+	struct drm_device *dev = connector->dev;
+	struct pci_dev *pdev = to_pci_dev(dev->dev);
+	const struct drm_edid *drm_edid;
+
+	if (drm_WARN_ON_ONCE(dev, !dev_is_pci(dev->dev)))
+		return NULL;
+
+	vga_switcheroo_lock_ddc(pdev);
+	drm_edid = drm_edid_read_ddc(connector, adapter);
+	vga_switcheroo_unlock_ddc(pdev);
+
+	return drm_edid;
+}
+EXPORT_SYMBOL(drm_edid_read_switcheroo);
+
 /**
  * drm_edid_duplicate - duplicate an EDID and the extensions
  * @edid: EDID to duplicate

include/drm/drm_edid.h

@@ -613,6 +613,8 @@ const struct drm_edid *drm_edid_read_ddc(struct drm_connector *connector,
 const struct drm_edid *drm_edid_read_custom(struct drm_connector *connector,
 					    int (*read_block)(void *context, u8 *buf, unsigned int block, size_t len),
 					    void *context);
+const struct drm_edid *drm_edid_read_switcheroo(struct drm_connector *connector,
+						struct i2c_adapter *adapter);
 int drm_edid_connector_update(struct drm_connector *connector,
 			      const struct drm_edid *edid);
 int drm_edid_connector_add_modes(struct drm_connector *connector);