drm/i915: VBT's child_device_config changes over time

[karo-tx-linux.git] / drivers / gpu / drm / i915 / intel_bios.h

diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
index 6e9250eb9c2c4b02fd2837d45420b2de2411b7ef..1da2bf208299727000116adef78d7802de4e2a5e 100644 (file)
--- a/drivers/gpu/drm/i915/intel_bios.h
+++ b/drivers/gpu/drm/i915/intel_bios.h
@@ -202,7 +202,10 @@ struct bdb_general_features {
 #define DEVICE_PORT_DVOB       0x01
 #define DEVICE_PORT_DVOC       0x02
 
-struct child_device_config {
+/* We used to keep this struct but without any version control. We should avoid
+ * using it in the future, but it should be safe to keep using it in the old
+ * code. */
+struct old_child_dev_config {
        u16 handle;
        u16 device_type;
        u8  device_id[10]; /* ascii string */
@@ -224,6 +227,32 @@ struct child_device_config {
        u8  dvo_function;
 } __attribute__((packed));
 
+/* This one contains field offsets that are known to be common for all BDB
+ * versions. Notice that the meaning of the contents contents may still change,
+ * but at least the offsets are consistent. */
+struct common_child_dev_config {
+       u16 handle;
+       u16 device_type;
+       u8 not_common1[12];
+       u8 dvo_port;
+       u8 not_common2[2];
+       u8 ddc_pin;
+       u16 edid_ptr;
+} __attribute__((packed));
+
+/* This field changes depending on the BDB version, so the most reliable way to
+ * read it is by checking the BDB version and reading the raw pointer. */
+union child_device_config {
+       /* This one is safe to be used anywhere, but the code should still check
+        * the BDB version. */
+       u8 raw[33];
+       /* This one should only be kept for legacy code. */
+       struct old_child_dev_config old;
+       /* This one should also be safe to use anywhere, even without version
+        * checks. */
+       struct common_child_dev_config common;
+};
+
 struct bdb_general_definitions {
        /* DDC GPIO */
        u8 crt_ddc_gmbus_pin;
@@ -249,7 +278,7 @@ struct bdb_general_definitions {
         * number = (block_size - sizeof(bdb_general_definitions))/
         *           sizeof(child_device_config);
         */
-       struct child_device_config devices[0];
+       union child_device_config devices[0];
 } __attribute__((packed));
 
 struct bdb_lvds_options {