[PATCH 0/2] drm: detect panel type from DisplayID 2.x

[PATCH 0/2] drm: detect panel type from DisplayID 2.x

[Chenyu Chen]

Parse the Display Device Technology field from the DisplayID v2.x
Display Parameters Data Block to identify LCD and OLED panels, and
wire it into amdgpu_dm as a fallback for panel type detection.

Chenyu Chen (2):
  drm/edid: parse panel type from DisplayID 2.x Display Parameters block
  drm/amd/display: use DisplayID panel type in dm_set_panel_type

 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 12 ++--
 drivers/gpu/drm/drm_displayid_internal.h      | 25 ++++++++
 drivers/gpu/drm/drm_edid.c                    | 61 +++++++++++++++----
 include/drm/drm_connector.h                   |  6 ++
 include/uapi/drm/drm_mode.h                   |  1 +
 5 files changed, 89 insertions(+), 16 deletions(-)

-- 
2.43.0

[PATCH 1/2] drm/edid: parse panel type from DisplayID 2.x Display Parameters block

[Chenyu Chen]

Parse the Display Parameters Data Block (tag 0x21) defined in
DisplayID v2.1a Section 4.2.6. Extract the Display Device Technology
field from payload byte 27, bits [6:4], which indicates whether the
panel is LCD (001b) or OLED (010b).

Store the result in drm_display_info.did_panel_type so that downstream
drivers can use it for panel-type-dependent behavior.

Assisted-by: Copilot:Claude-Opus-4.6
Signed-off-by: Chenyu Chen <chen-yu.chen@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/gpu/drm/drm_displayid_internal.h | 25 ++++++++++
 drivers/gpu/drm/drm_edid.c               | 61 +++++++++++++++++++-----
 include/drm/drm_connector.h              |  6 +++
 include/uapi/drm/drm_mode.h              |  1 +
 4 files changed, 82 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_displayid_internal.h b/drivers/gpu/drm/drm_displayid_internal.h
index 5b1b32f73516..e0f7c54d2987 100644
--- a/drivers/gpu/drm/drm_displayid_internal.h
+++ b/drivers/gpu/drm/drm_displayid_internal.h
@@ -142,6 +142,31 @@ struct displayid_formula_timing_block {
 	struct displayid_formula_timings_9 timings[];
 } __packed;
 
+/*
+ * DisplayID v2.x Display Parameters Data Block (tag 0x21).
+ *
+ * Per VESA DisplayID v2.1a, Section 4.2.6, Table 4-14:
+ * Offset 0x1E (payload byte 27) contains Native Color Depth and
+ * Display Device Technology fields.
+ *   bits [2:0] = Native Color Depth
+ *   bit  [3]   = RESERVED
+ *   bits [6:4] = Display Device Technology
+ *     000b = not specified, 001b = LCD, 010b = OLED, others reserved
+ *   bit  [7]   = Display Device Theme Preference
+ */
+#define DISPLAYID_DISPLAY_PARAMS_DEVICE_TECH	GENMASK(6, 4)
+
+struct displayid_display_params_block {
+	struct displayid_block base;
+	u8 payload[27];
+	u8 device_tech_byte; /* bits [6:4] = Display Device Technology */
+	u8 reserved;
+} __packed;
+
+#define DISPLAYID_DISPLAY_PARAMS_MIN_LEN	\
+	(sizeof(struct displayid_display_params_block) -	\
+	 sizeof(struct displayid_block))
+
 #define DISPLAYID_VESA_MSO_OVERLAP	GENMASK(3, 0)
 #define DISPLAYID_VESA_MSO_MODE		GENMASK(6, 5)
 
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 8031f021d4d0..9b160a878df4 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -6713,6 +6713,8 @@ static void drm_reset_display_info(struct drm_connector *connector)
 
 	info->source_physical_address = CEC_PHYS_ADDR_INVALID;
 	memset(&info->amd_vsdb, 0, sizeof(info->amd_vsdb));
+
+	info->did_panel_type = DRM_MODE_PANEL_TYPE_UNKNOWN;
 }
 
 static void update_displayid_info(struct drm_connector *connector,
@@ -6721,24 +6723,61 @@ static void update_displayid_info(struct drm_connector *connector,
 	struct drm_display_info *info = &connector->display_info;
 	const struct displayid_block *block;
 	struct displayid_iter iter;
+	const u8 *section = NULL;
 
 	displayid_iter_edid_begin(drm_edid, &iter);
 	displayid_iter_for_each(block, &iter) {
+		if (section != iter.section) {
+			drm_dbg_kms(connector->dev,
+				    "[CONNECTOR:%d:%s] DisplayID extension version 0x%02x, primary use 0x%02x\n",
+				    connector->base.id, connector->name,
+				    displayid_version(&iter),
+				    displayid_primary_use(&iter));
+			if (displayid_version(&iter) == DISPLAY_ID_STRUCTURE_VER_20 &&
+			    (displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_VR ||
+			     displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_AR))
+				info->non_desktop = true;
+			section = iter.section;
+		}
+
 		drm_dbg_kms(connector->dev,
-			    "[CONNECTOR:%d:%s] DisplayID extension version 0x%02x, primary use 0x%02x\n",
+			    "[CONNECTOR:%d:%s] DisplayID block tag 0x%02x, rev 0x%02x, size %u\n",
 			    connector->base.id, connector->name,
-			    displayid_version(&iter),
-			    displayid_primary_use(&iter));
+			    block->tag, block->rev, block->num_bytes);
+
 		if (displayid_version(&iter) == DISPLAY_ID_STRUCTURE_VER_20 &&
-		    (displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_VR ||
-		     displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_AR))
-			info->non_desktop = true;
+		    block->tag == DATA_BLOCK_2_DISPLAY_PARAMETERS) {
+			const struct displayid_display_params_block *params =
+				(const struct displayid_display_params_block *)block;
+			u8 tech;
+
+			if (block->num_bytes < DISPLAYID_DISPLAY_PARAMS_MIN_LEN) {
+				drm_dbg_kms(connector->dev,
+					    "[CONNECTOR:%d:%s] DisplayID Display Parameters block too short (%u < %zu)\n",
+					    connector->base.id, connector->name,
+					    block->num_bytes,
+					    DISPLAYID_DISPLAY_PARAMS_MIN_LEN);
+				continue;
+			}
 
-		/*
-		 * We're only interested in the base section here, no need to
-		 * iterate further.
-		 */
-		break;
+			tech = FIELD_GET(DISPLAYID_DISPLAY_PARAMS_DEVICE_TECH,
+					 params->device_tech_byte);
+
+			drm_dbg_kms(connector->dev,
+				    "[CONNECTOR:%d:%s] DisplayID Display Parameters: device technology %u\n",
+				    connector->base.id, connector->name, tech);
+
+			switch (tech) {
+			case 1: /* LCD */
+				info->did_panel_type = DRM_MODE_PANEL_TYPE_LCD;
+				break;
+			case 2: /* OLED */
+				info->did_panel_type = DRM_MODE_PANEL_TYPE_OLED;
+				break;
+			default:
+				break;
+			}
+		}
 	}
 	displayid_iter_end(&iter);
 }
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index c398dbc68bbc..b95aec34ddb7 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -899,6 +899,12 @@ struct drm_display_info {
 	 * @amd_vsdb: AMD-specific VSDB information.
 	 */
 	struct drm_amd_vsdb_info amd_vsdb;
+
+	/**
+	 * @did_panel_type: Panel type from DisplayID Display Parameters
+	 * Data Block (tag 0x21). Uses DRM_MODE_PANEL_TYPE_* constants.
+	 */
+	u8 did_panel_type;
 };
 
 int drm_display_info_set_bus_formats(struct drm_display_info *info,
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 3693d82b5279..d7ca1040b92e 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -169,6 +169,7 @@ extern "C" {
 /* Panel type property */
 #define DRM_MODE_PANEL_TYPE_UNKNOWN	0
 #define DRM_MODE_PANEL_TYPE_OLED	1
+#define DRM_MODE_PANEL_TYPE_LCD		2
 
 /*
  * DRM_MODE_ROTATE_<degrees>
-- 
2.43.0

Re: [PATCH 1/2] drm/edid: parse panel type from DisplayID 2.x Display Parameters block

[Jani Nikula]

On Thu, 14 May 2026, Chenyu Chen <chen-yu.chen@amd.com> wrote:
> Parse the Display Parameters Data Block (tag 0x21) defined in
> DisplayID v2.1a Section 4.2.6. Extract the Display Device Technology
> field from payload byte 27, bits [6:4], which indicates whether the
> panel is LCD (001b) or OLED (010b).
>
> Store the result in drm_display_info.did_panel_type so that downstream
> drivers can use it for panel-type-dependent behavior.
>
> Assisted-by: Copilot:Claude-Opus-4.6
> Signed-off-by: Chenyu Chen <chen-yu.chen@amd.com>
> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>  drivers/gpu/drm/drm_displayid_internal.h | 25 ++++++++++
>  drivers/gpu/drm/drm_edid.c               | 61 +++++++++++++++++++-----
>  include/drm/drm_connector.h              |  6 +++
>  include/uapi/drm/drm_mode.h              |  1 +
>  4 files changed, 82 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_displayid_internal.h b/drivers/gpu/drm/drm_displayid_internal.h
> index 5b1b32f73516..e0f7c54d2987 100644
> --- a/drivers/gpu/drm/drm_displayid_internal.h
> +++ b/drivers/gpu/drm/drm_displayid_internal.h
> @@ -142,6 +142,31 @@ struct displayid_formula_timing_block {
>  	struct displayid_formula_timings_9 timings[];
>  } __packed;
>  
> +/*
> + * DisplayID v2.x Display Parameters Data Block (tag 0x21).
> + *
> + * Per VESA DisplayID v2.1a, Section 4.2.6, Table 4-14:
> + * Offset 0x1E (payload byte 27) contains Native Color Depth and
> + * Display Device Technology fields.
> + *   bits [2:0] = Native Color Depth
> + *   bit  [3]   = RESERVED
> + *   bits [6:4] = Display Device Technology
> + *     000b = not specified, 001b = LCD, 010b = OLED, others reserved
> + *   bit  [7]   = Display Device Theme Preference
> + */
> +#define DISPLAYID_DISPLAY_PARAMS_DEVICE_TECH	GENMASK(6, 4)
> +
> +struct displayid_display_params_block {
> +	struct displayid_block base;
> +	u8 payload[27];
> +	u8 device_tech_byte; /* bits [6:4] = Display Device Technology */
> +	u8 reserved;
> +} __packed;
> +
> +#define DISPLAYID_DISPLAY_PARAMS_MIN_LEN	\
> +	(sizeof(struct displayid_display_params_block) -	\
> +	 sizeof(struct displayid_block))
> +
>  #define DISPLAYID_VESA_MSO_OVERLAP	GENMASK(3, 0)
>  #define DISPLAYID_VESA_MSO_MODE		GENMASK(6, 5)
>  
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 8031f021d4d0..9b160a878df4 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -6713,6 +6713,8 @@ static void drm_reset_display_info(struct drm_connector *connector)
>  
>  	info->source_physical_address = CEC_PHYS_ADDR_INVALID;
>  	memset(&info->amd_vsdb, 0, sizeof(info->amd_vsdb));
> +
> +	info->did_panel_type = DRM_MODE_PANEL_TYPE_UNKNOWN;
>  }
>  
>  static void update_displayid_info(struct drm_connector *connector,
> @@ -6721,24 +6723,61 @@ static void update_displayid_info(struct drm_connector *connector,
>  	struct drm_display_info *info = &connector->display_info;
>  	const struct displayid_block *block;
>  	struct displayid_iter iter;
> +	const u8 *section = NULL;
>  
>  	displayid_iter_edid_begin(drm_edid, &iter);
>  	displayid_iter_for_each(block, &iter) {
> +		if (section != iter.section) {
> +			drm_dbg_kms(connector->dev,
> +				    "[CONNECTOR:%d:%s] DisplayID extension version 0x%02x, primary use 0x%02x\n",
> +				    connector->base.id, connector->name,
> +				    displayid_version(&iter),
> +				    displayid_primary_use(&iter));
> +			if (displayid_version(&iter) == DISPLAY_ID_STRUCTURE_VER_20 &&
> +			    (displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_VR ||
> +			     displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_AR))
> +				info->non_desktop = true;
> +			section = iter.section;
> +		}

What is this even supposed to do?

> +
>  		drm_dbg_kms(connector->dev,
> -			    "[CONNECTOR:%d:%s] DisplayID extension version 0x%02x, primary use 0x%02x\n",
> +			    "[CONNECTOR:%d:%s] DisplayID block tag 0x%02x, rev 0x%02x, size %u\n",
>  			    connector->base.id, connector->name,
> -			    displayid_version(&iter),
> -			    displayid_primary_use(&iter));
> +			    block->tag, block->rev, block->num_bytes);
> +
>  		if (displayid_version(&iter) == DISPLAY_ID_STRUCTURE_VER_20 &&
> -		    (displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_VR ||
> -		     displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_AR))
> -			info->non_desktop = true;
> +		    block->tag == DATA_BLOCK_2_DISPLAY_PARAMETERS) {
> +			const struct displayid_display_params_block *params =
> +				(const struct displayid_display_params_block *)block;
> +			u8 tech;
> +
> +			if (block->num_bytes < DISPLAYID_DISPLAY_PARAMS_MIN_LEN) {
> +				drm_dbg_kms(connector->dev,
> +					    "[CONNECTOR:%d:%s] DisplayID Display Parameters block too short (%u < %zu)\n",
> +					    connector->base.id, connector->name,
> +					    block->num_bytes,
> +					    DISPLAYID_DISPLAY_PARAMS_MIN_LEN);
> +				continue;
> +			}
>  
> -		/*
> -		 * We're only interested in the base section here, no need to
> -		 * iterate further.
> -		 */
> -		break;
> +			tech = FIELD_GET(DISPLAYID_DISPLAY_PARAMS_DEVICE_TECH,
> +					 params->device_tech_byte);
> +
> +			drm_dbg_kms(connector->dev,
> +				    "[CONNECTOR:%d:%s] DisplayID Display Parameters: device technology %u\n",
> +				    connector->base.id, connector->name, tech);
> +
> +			switch (tech) {
> +			case 1: /* LCD */
> +				info->did_panel_type = DRM_MODE_PANEL_TYPE_LCD;
> +				break;
> +			case 2: /* OLED */
> +				info->did_panel_type = DRM_MODE_PANEL_TYPE_OLED;
> +				break;
> +			default:
> +				break;
> +			}
> +		}

Please tell copilot to not add so much crap in the iterator block. Add
functions. Add the first function as a refactor for non_desktop, add
more stuff on top, i.e. split this into multiple patches.

BR,
Jani.


>  	}
>  	displayid_iter_end(&iter);
>  }
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index c398dbc68bbc..b95aec34ddb7 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -899,6 +899,12 @@ struct drm_display_info {
>  	 * @amd_vsdb: AMD-specific VSDB information.
>  	 */
>  	struct drm_amd_vsdb_info amd_vsdb;
> +
> +	/**
> +	 * @did_panel_type: Panel type from DisplayID Display Parameters
> +	 * Data Block (tag 0x21). Uses DRM_MODE_PANEL_TYPE_* constants.
> +	 */
> +	u8 did_panel_type;
>  };
>  
>  int drm_display_info_set_bus_formats(struct drm_display_info *info,
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 3693d82b5279..d7ca1040b92e 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -169,6 +169,7 @@ extern "C" {
>  /* Panel type property */
>  #define DRM_MODE_PANEL_TYPE_UNKNOWN	0
>  #define DRM_MODE_PANEL_TYPE_OLED	1
> +#define DRM_MODE_PANEL_TYPE_LCD		2
>  
>  /*
>   * DRM_MODE_ROTATE_<degrees>

-- 
Jani Nikula, Intel

Re: [PATCH 1/2] drm/edid: parse panel type from DisplayID 2.x Display Parameters block

[Leo Li]

On 2026-05-15 04:23, Jani Nikula wrote:
> On Thu, 14 May 2026, Chenyu Chen <chen-yu.chen@amd.com> wrote:
>> Parse the Display Parameters Data Block (tag 0x21) defined in
>> DisplayID v2.1a Section 4.2.6. Extract the Display Device Technology
>> field from payload byte 27, bits [6:4], which indicates whether the
>> panel is LCD (001b) or OLED (010b).
>>
>> Store the result in drm_display_info.did_panel_type so that downstream
>> drivers can use it for panel-type-dependent behavior.
>>
>> Assisted-by: Copilot:Claude-Opus-4.6
>> Signed-off-by: Chenyu Chen <chen-yu.chen@amd.com>
>> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>>  drivers/gpu/drm/drm_displayid_internal.h | 25 ++++++++++
>>  drivers/gpu/drm/drm_edid.c               | 61 +++++++++++++++++++-----
>>  include/drm/drm_connector.h              |  6 +++
>>  include/uapi/drm/drm_mode.h              |  1 +
>>  4 files changed, 82 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_displayid_internal.h b/drivers/gpu/drm/drm_displayid_internal.h
>> index 5b1b32f73516..e0f7c54d2987 100644
>> --- a/drivers/gpu/drm/drm_displayid_internal.h
>> +++ b/drivers/gpu/drm/drm_displayid_internal.h
>> @@ -142,6 +142,31 @@ struct displayid_formula_timing_block {
>>  	struct displayid_formula_timings_9 timings[];
>>  } __packed;
>>  
>> +/*
>> + * DisplayID v2.x Display Parameters Data Block (tag 0x21).
>> + *
>> + * Per VESA DisplayID v2.1a, Section 4.2.6, Table 4-14:
>> + * Offset 0x1E (payload byte 27) contains Native Color Depth and
>> + * Display Device Technology fields.
>> + *   bits [2:0] = Native Color Depth
>> + *   bit  [3]   = RESERVED
>> + *   bits [6:4] = Display Device Technology
>> + *     000b = not specified, 001b = LCD, 010b = OLED, others reserved
>> + *   bit  [7]   = Display Device Theme Preference
>> + */
>> +#define DISPLAYID_DISPLAY_PARAMS_DEVICE_TECH	GENMASK(6, 4)
>> +
>> +struct displayid_display_params_block {
>> +	struct displayid_block base;
>> +	u8 payload[27];
>> +	u8 device_tech_byte; /* bits [6:4] = Display Device Technology */
>> +	u8 reserved;
>> +} __packed;
>> +
>> +#define DISPLAYID_DISPLAY_PARAMS_MIN_LEN	\
>> +	(sizeof(struct displayid_display_params_block) -	\
>> +	 sizeof(struct displayid_block))
>> +
>>  #define DISPLAYID_VESA_MSO_OVERLAP	GENMASK(3, 0)
>>  #define DISPLAYID_VESA_MSO_MODE		GENMASK(6, 5)
>>  
>> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
>> index 8031f021d4d0..9b160a878df4 100644
>> --- a/drivers/gpu/drm/drm_edid.c
>> +++ b/drivers/gpu/drm/drm_edid.c
>> @@ -6713,6 +6713,8 @@ static void drm_reset_display_info(struct drm_connector *connector)
>>  
>>  	info->source_physical_address = CEC_PHYS_ADDR_INVALID;
>>  	memset(&info->amd_vsdb, 0, sizeof(info->amd_vsdb));
>> +
>> +	info->did_panel_type = DRM_MODE_PANEL_TYPE_UNKNOWN;
>>  }
>>  
>>  static void update_displayid_info(struct drm_connector *connector,
>> @@ -6721,24 +6723,61 @@ static void update_displayid_info(struct drm_connector *connector,
>>  	struct drm_display_info *info = &connector->display_info;
>>  	const struct displayid_block *block;
>>  	struct displayid_iter iter;
>> +	const u8 *section = NULL;
>>  
>>  	displayid_iter_edid_begin(drm_edid, &iter);
>>  	displayid_iter_for_each(block, &iter) {
>> +		if (section != iter.section) {
>> +			drm_dbg_kms(connector->dev,
>> +				    "[CONNECTOR:%d:%s] DisplayID extension version 0x%02x, primary use 0x%02x\n",
>> +				    connector->base.id, connector->name,
>> +				    displayid_version(&iter),
>> +				    displayid_primary_use(&iter));
>> +			if (displayid_version(&iter) == DISPLAY_ID_STRUCTURE_VER_20 &&
>> +			    (displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_VR ||
>> +			     displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_AR))
>> +				info->non_desktop = true;
>> +			section = iter.section;
>> +		}
> 
> What is this even supposed to do?
> 

I think the intention is to log and process the DisplayID base section header only once instead on every
iteration. Maybe a `bool header_processed` works better?

- Leo

>> +
>>  		drm_dbg_kms(connector->dev,
>> -			    "[CONNECTOR:%d:%s] DisplayID extension version 0x%02x, primary use 0x%02x\n",
>> +			    "[CONNECTOR:%d:%s] DisplayID block tag 0x%02x, rev 0x%02x, size %u\n",
>>  			    connector->base.id, connector->name,
>> -			    displayid_version(&iter),
>> -			    displayid_primary_use(&iter));
>> +			    block->tag, block->rev, block->num_bytes);
>> +
>>  		if (displayid_version(&iter) == DISPLAY_ID_STRUCTURE_VER_20 &&
>> -		    (displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_VR ||
>> -		     displayid_primary_use(&iter) == PRIMARY_USE_HEAD_MOUNTED_AR))
>> -			info->non_desktop = true;
>> +		    block->tag == DATA_BLOCK_2_DISPLAY_PARAMETERS) {
>> +			const struct displayid_display_params_block *params =
>> +				(const struct displayid_display_params_block *)block;
>> +			u8 tech;
>> +
>> +			if (block->num_bytes < DISPLAYID_DISPLAY_PARAMS_MIN_LEN) {
>> +				drm_dbg_kms(connector->dev,
>> +					    "[CONNECTOR:%d:%s] DisplayID Display Parameters block too short (%u < %zu)\n",
>> +					    connector->base.id, connector->name,
>> +					    block->num_bytes,
>> +					    DISPLAYID_DISPLAY_PARAMS_MIN_LEN);
>> +				continue;
>> +			}
>>  
>> -		/*
>> -		 * We're only interested in the base section here, no need to
>> -		 * iterate further.
>> -		 */
>> -		break;
>> +			tech = FIELD_GET(DISPLAYID_DISPLAY_PARAMS_DEVICE_TECH,
>> +					 params->device_tech_byte);
>> +
>> +			drm_dbg_kms(connector->dev,
>> +				    "[CONNECTOR:%d:%s] DisplayID Display Parameters: device technology %u\n",
>> +				    connector->base.id, connector->name, tech);
>> +
>> +			switch (tech) {
>> +			case 1: /* LCD */
>> +				info->did_panel_type = DRM_MODE_PANEL_TYPE_LCD;
>> +				break;
>> +			case 2: /* OLED */
>> +				info->did_panel_type = DRM_MODE_PANEL_TYPE_OLED;
>> +				break;
>> +			default:
>> +				break;
>> +			}
>> +		}
> 
> Please tell copilot to not add so much crap in the iterator block. Add
> functions. Add the first function as a refactor for non_desktop, add
> more stuff on top, i.e. split this into multiple patches.
> 
> BR,
> Jani.
> 
> 
>>  	}
>>  	displayid_iter_end(&iter);
>>  }
>> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
>> index c398dbc68bbc..b95aec34ddb7 100644
>> --- a/include/drm/drm_connector.h
>> +++ b/include/drm/drm_connector.h
>> @@ -899,6 +899,12 @@ struct drm_display_info {
>>  	 * @amd_vsdb: AMD-specific VSDB information.
>>  	 */
>>  	struct drm_amd_vsdb_info amd_vsdb;
>> +
>> +	/**
>> +	 * @did_panel_type: Panel type from DisplayID Display Parameters
>> +	 * Data Block (tag 0x21). Uses DRM_MODE_PANEL_TYPE_* constants.
>> +	 */
>> +	u8 did_panel_type;
>>  };
>>  
>>  int drm_display_info_set_bus_formats(struct drm_display_info *info,
>> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
>> index 3693d82b5279..d7ca1040b92e 100644
>> --- a/include/uapi/drm/drm_mode.h
>> +++ b/include/uapi/drm/drm_mode.h
>> @@ -169,6 +169,7 @@ extern "C" {
>>  /* Panel type property */
>>  #define DRM_MODE_PANEL_TYPE_UNKNOWN	0
>>  #define DRM_MODE_PANEL_TYPE_OLED	1
>> +#define DRM_MODE_PANEL_TYPE_LCD		2
>>  
>>  /*
>>   * DRM_MODE_ROTATE_<degrees>
> 

Claude review: drm/edid: parse panel type from DisplayID 2.x Display Parameters block

[Claude Code Review Bot]

Patch Review

**Struct layout and minimum length check — looks correct.**

The `displayid_display_params_block` struct places `device_tech_byte` at payload offset 27 (absolute block offset 0x1E), matching the spec reference. The `DISPLAYID_DISPLAY_PARAMS_MIN_LEN` correctly computes 29 (the struct payload excluding the `displayid_block` header), ensuring `device_tech_byte` is accessible before it's read:

```c
if (block->num_bytes < DISPLAYID_DISPLAY_PARAMS_MIN_LEN) {
    ...
    continue;
}
```

**Private field access in `displayid_iter`.**

The patch accesses `iter.section` directly:

```c
const u8 *section = NULL;
...
if (section != iter.section) {
    ...
    section = iter.section;
}
```

The `displayid_iter` struct is annotated with `Do not access directly, this is private.` While `drm_edid.c` is core DRM code and uses the internal header, this still violates the stated API contract. Consider adding an accessor like `displayid_section()` alongside the existing `displayid_version()` and `displayid_primary_use()`. Alternatively, a boolean `displayid_is_v2_headmount()` helper that encapsulates the VR/AR check might be cleaner, so the section-tracking remains internal to the iterator implementation.

**Behavior change from removing the `break` — intentional but worth noting in the commit message.**

The old code:
```c
displayid_iter_for_each(block, &iter) {
    // log + VR/AR check
    break;  // only first block of first section
}
```

The new code iterates **all blocks across all sections**. This is required to find the Display Parameters block, and the VR/AR detection is correctly refactored to fire once per section via the `section` pointer guard. However, the commit message doesn't mention this change in iteration scope. It would be helpful to note that the function now processes all DisplayID sections/blocks, not just the first.

**Minor: magic numbers in the switch.**

```c
case 1: /* LCD */
    info->did_panel_type = DRM_MODE_PANEL_TYPE_LCD;
    break;
case 2: /* OLED */
    info->did_panel_type = DRM_MODE_PANEL_TYPE_OLED;
    break;
```

These match the spec (Display Device Technology: 001b = LCD, 010b = OLED). The comments are sufficient, but named constants in the header (e.g. `DISPLAYID_DEVICE_TECH_LCD = 1`, `DISPLAYID_DEVICE_TECH_OLED = 2`) would be slightly more self-documenting and consistent with the kernel style for spec-derived values.

**Missing update to `drm_panel_type_enum_list`.**

The new `DRM_MODE_PANEL_TYPE_LCD` value is added to `drm_mode.h` but the enum registration in `drm_connector.c` is not updated:

```c
static const struct drm_prop_enum_list drm_panel_type_enum_list[] = {
    { DRM_MODE_PANEL_TYPE_UNKNOWN, "unknown" },
    { DRM_MODE_PANEL_TYPE_OLED, "OLED" },
    // missing: { DRM_MODE_PANEL_TYPE_LCD, "LCD" },
};
```

Without this, `DRM_MODE_PANEL_TYPE_LCD` cannot actually be used as a property value. This should be part of this patch (since this is where the UAPI constant is introduced).

**Overall:** Structurally solid parsing code, but needs the enum list update and preferably an accessor for `iter.section`.

---

---
Generated by Claude Code Patch Reviewer

[PATCH 2/2] drm/amd/display: use DisplayID panel type in dm_set_panel_type

[Chenyu Chen]

Wire up the newly parsed did_panel_type from drm_display_info into
amdgpu_dm's panel type detection path. When neither the AMD VSDB
nor DPCD determines the panel type, fall back to the DisplayID
Display Device Technology field to set PANEL_TYPE_LCD or
PANEL_TYPE_OLED accordingly.

Assisted-by: Copilot:Claude-Opus-4.6
Signed-off-by: Chenyu Chen <chen-yu.chen@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index e42a5eecdf46..353a4982333d 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3944,11 +3944,13 @@ static void dm_set_panel_type(struct amdgpu_dm_connector *aconnector)
 			link->panel_type = PANEL_TYPE_OLED;
 	}
 
-	/*
-	 * TODO: get panel type from DID2 that has device technology field
-	 * to specify if it's OLED or not. But we need to wait for DID2
-	 * support in DC and EDID parser to be able to use it here.
-	 */
+	/* If VSDB and DPCD didn't determine panel type, check DID */
+	if (link->panel_type == PANEL_TYPE_NONE) {
+		if (display_info->did_panel_type == DRM_MODE_PANEL_TYPE_LCD)
+			link->panel_type = PANEL_TYPE_LCD;
+		else if (display_info->did_panel_type == DRM_MODE_PANEL_TYPE_OLED)
+			link->panel_type = PANEL_TYPE_OLED;
+	}
 
 	if (link->panel_type == PANEL_TYPE_NONE) {
 		struct drm_amd_vsdb_info *vsdb = &display_info->amd_vsdb;
-- 
2.43.0

Claude review: drm/amd/display: use DisplayID panel type in dm_set_panel_type

[Claude Code Review Bot]

Patch Review

**Placement of the DID2 fallback — correct.**

The new check is inserted after VSDB + DPCD and before the Samsung heuristic, which matches the priority the TODO comment described:

```c
/* If VSDB and DPCD didn't determine panel type, check DID */
if (link->panel_type == PANEL_TYPE_NONE) {
    if (display_info->did_panel_type == DRM_MODE_PANEL_TYPE_LCD)
        link->panel_type = PANEL_TYPE_LCD;
    else if (display_info->did_panel_type == DRM_MODE_PANEL_TYPE_OLED)
        link->panel_type = PANEL_TYPE_OLED;
}
```

This correctly gates on `PANEL_TYPE_NONE`, so higher-priority detection (VSDB, DPCD) is not overridden.

**Bug: property-setting code not updated for LCD.**

The existing code at the end of `dm_set_panel_type()` (untouched by this patch) is:

```c
if (link->panel_type == PANEL_TYPE_OLED)
    drm_object_property_set_value(&connector->base,
        adev_to_drm(adev)->mode_config.panel_type_property,
        DRM_MODE_PANEL_TYPE_OLED);
else
    drm_object_property_set_value(&connector->base,
        adev_to_drm(adev)->mode_config.panel_type_property,
        DRM_MODE_PANEL_TYPE_UNKNOWN);
```

If DID2 detects LCD, `link->panel_type` becomes `PANEL_TYPE_LCD` (value 1 from `dc_types.h`). This falls into the `else` branch, and the userspace-visible property is set to `DRM_MODE_PANEL_TYPE_UNKNOWN`. The LCD detection works internally within the driver but is invisible to userspace.

This should be updated to also handle `PANEL_TYPE_LCD`:

```c
if (link->panel_type == PANEL_TYPE_OLED)
    ...DRM_MODE_PANEL_TYPE_OLED;
else if (link->panel_type == PANEL_TYPE_LCD)
    ...DRM_MODE_PANEL_TYPE_LCD;
else
    ...DRM_MODE_PANEL_TYPE_UNKNOWN;
```

**Style nit: mixing UAPI and internal constants in the comparison.**

```c
if (display_info->did_panel_type == DRM_MODE_PANEL_TYPE_LCD)
    link->panel_type = PANEL_TYPE_LCD;
```

This compares a `DRM_MODE_PANEL_TYPE_*` (UAPI) value against the same namespace and assigns a `PANEL_TYPE_*` (DC internal) value. It works because the values happen to map correctly, but it couples the driver to the UAPI constants. The `did_panel_type` field in `drm_display_info` uses UAPI constants by design (it's DRM core), so this cross-namespace mapping is unavoidable here. Just be aware that if either namespace is reordered independently, this breaks silently.

**Overall:** The fallback logic is correct and well-placed. The missing property-setting update for LCD is the main issue that should be fixed before merging.

---
Generated by Claude Code Patch Reviewer

Claude review: drm: detect panel type from DisplayID 2.x

[Claude Code Review Bot]

Overall Series Review

Subject: drm: detect panel type from DisplayID 2.x
Author: Chenyu Chen <chen-yu.chen@amd.com>
Patches: 5
Reviewed: 2026-05-16T11:17:30.013253

---

This 2-patch series adds DisplayID v2.x Display Parameters Data Block parsing to detect LCD vs OLED panels, and wires it into amdgpu_dm as a fallback panel type detection path. The general approach is sound: it fills a longstanding TODO in the amdgpu_dm code.

**However, there is a significant gap across the series:** `DRM_MODE_PANEL_TYPE_LCD` is added to the UAPI header (`drm_mode.h`) but:
1. The `drm_panel_type_enum_list` in `drm_connector.c` is not updated to include LCD, so the `panel_type` property enum doesn't recognize value 2.
2. The property-setting code at the end of `dm_set_panel_type()` is not updated to expose LCD — it only maps `PANEL_TYPE_OLED` → `DRM_MODE_PANEL_TYPE_OLED` and everything else → `DRM_MODE_PANEL_TYPE_UNKNOWN`.

This means a DID2-detected LCD panel will correctly set `link->panel_type = PANEL_TYPE_LCD` internally, but userspace will see `DRM_MODE_PANEL_TYPE_UNKNOWN` from the property, and the enum property likely cannot even accept value 2. The new UAPI constant is effectively dead code.

---

---
Generated by Claude Code Patch Reviewer