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Fri, 15 May 2026 18:47:09 -0500 Received: from [10.4.12.198] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.41 via Frontend Transport; Fri, 15 May 2026 18:47:08 -0500 Message-ID: <020f60b5-b2c4-494a-a16d-07a700d299f4@amd.com> Date: Fri, 15 May 2026 19:47:08 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] drm/edid: parse panel type from DisplayID 2.x Display Parameters block To: Jani Nikula , Chenyu Chen , , CC: Harry Wentland , Ray Wu , Limonciello Mario References: <20260514065606.1151834-1-chen-yu.chen@amd.com> <20260514065606.1151834-2-chen-yu.chen@amd.com> <8e0c6356a570c55e3df54be6c2d7952dfcee2a06@intel.com> Content-Language: en-US From: Leo Li In-Reply-To: <8e0c6356a570c55e3df54be6c2d7952dfcee2a06@intel.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Received-SPF: None (SATLEXMB04.amd.com: sunpeng.li@amd.com does not designate permitted sender hosts) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS2PEPF00003448:EE_|CH3PR12MB8076:EE_ X-MS-Office365-Filtering-Correlation-Id: 4f3d2ffc-4555-4840-496d-08deb2dc4786 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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Ip=[165.204.84.17]; Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DS2PEPF00003448.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB8076 X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" On 2026-05-15 04:23, Jani Nikula wrote: > On Thu, 14 May 2026, Chenyu Chen 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 >> Reviewed-by: Mario Limonciello >> --- >> 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_ >