drm/edid: Allow querying/working with the panel ID from the EDID

EDIDs have 32-bits worth of data which is intended to be used to
uniquely identify the make/model of a panel. This has historically
been used only internally in the EDID processing code to identify
quirks with panels.

We'd like to use this panel ID in panel drivers to identify which
panel is hooked up and from that information figure out power sequence
timings. Let's expose this information from the EDID code and also
allow it to be accessed early, before a connector has been created.

To make matching in the panel drivers code easier, we'll return the
panel ID as a 32-bit value. We'll provide some functions for
converting this value back and forth to something more human readable.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210914132020.v5.3.I4a672175ba1894294d91d3dbd51da11a8239cf4a@changeid

1 files changed, 45 insertions, 0 deletions

diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index deccfd39e6db..ccc80cb7f86a 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -508,6 +508,50 @@ static inline u8 drm_eld_get_conn_type(const uint8_t *eld)
 	return eld[DRM_ELD_SAD_COUNT_CONN_TYPE] & DRM_ELD_CONN_TYPE_MASK;
 }
 
+/**
+ * drm_edid_encode_panel_id - Encode an ID for matching against drm_edid_get_panel_id()
+ * @vend: 3-character vendor string
+ * @product_id: The 16-bit product ID.
+ *
+ * This is a macro so that it can be calculated at compile time and used
+ * as an initializer.
+ *
+ * For instance:
+ *   drm_edid_encode_panel_id("BOE", 0x2d08) => 0x09e52d08
+ *
+ * Return: a 32-bit ID per panel.
+ */
+#define drm_edid_encode_panel_id(vend, product_id) \
+	((((u32)((vend)[0]) - '@') & 0x1f) << 26 | \
+	 (((u32)((vend)[1]) - '@') & 0x1f) << 21 | \
+	 (((u32)((vend)[2]) - '@') & 0x1f) << 16 | \
+	 ((product_id) & 0xffff))
+
+/**
+ * drm_edid_decode_panel_id - Decode a panel ID from drm_edid_encode_panel_id()
+ * @panel_id: The panel ID to decode.
+ * @vend: A 4-byte buffer to store the 3-letter vendor string plus a '\0'
+ *	  termination
+ * @product_id: The product ID will be returned here.
+ *
+ * For instance, after:
+ *   drm_edid_decode_panel_id(0x09e52d08, vend, &product_id)
+ * These will be true:
+ *   vend[0] = 'B'
+ *   vend[1] = 'O'
+ *   vend[2] = 'E'
+ *   vend[3] = '\0'
+ *   product_id = 0x2d08
+ */
+static inline void drm_edid_decode_panel_id(u32 panel_id, char vend[4], u16 *product_id)
+{
+	*product_id = (u16)(panel_id & 0xffff);
+	vend[0] = '@' + ((panel_id >> 26) & 0x1f);
+	vend[1] = '@' + ((panel_id >> 21) & 0x1f);
+	vend[2] = '@' + ((panel_id >> 16) & 0x1f);
+	vend[3] = '\0';
+}
+
 bool drm_probe_ddc(struct i2c_adapter *adapter);
 struct edid *drm_do_get_edid(struct drm_connector *connector,
 	int (*get_edid_block)(void *data, u8 *buf, unsigned int block,
@@ -515,6 +559,7 @@ 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);
+u32 drm_edid_get_panel_id(struct i2c_adapter *adapter);
 struct edid *drm_get_edid_switcheroo(struct drm_connector *connector,
 				     struct i2c_adapter *adapter);
 struct edid *drm_edid_duplicate(const struct edid *edid);