On Thu, 14 May 2026, Chenyu Chen <[email protected]> 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 <[email protected]>
> Reviewed-by: Mario Limonciello <[email protected]>
> ---
> 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
