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Message-ID: <f41cb5f2-1702-499e-81d9-8ce74537bf3f@linaro.org>
Date: Wed, 26 Nov 2025 09:16:43 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: kernel test robot <lkp@...el.com>,
Ludovic Desroches <ludovic.desroches@...rochip.com>,
Jessica Zhang <jesszhan0024@...il.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Anusha Srivatsa <asrivats@...hat.com>,
Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Subject: Re: [PATCH REGRESSION] drm/panel: simple: restore connector_type
fallback
Hi,
On 11/22/25 21:26, kernel test robot wrote:
> Hi Ludovic,
>
> kernel test robot noticed the following build warnings:
>
> [auto build test WARNING on 88cbd8ac379cf5ce68b7efcfd4d1484a6871ee0b]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Ludovic-Desroches/drm-panel-simple-restore-connector_type-fallback/20251121-212613
> base: 88cbd8ac379cf5ce68b7efcfd4d1484a6871ee0b
> patch link: https://lore.kernel.org/r/20251121-lcd_panel_connector_type_fix-v1-1-fdbbef34a1a4%40microchip.com
> patch subject: [PATCH REGRESSION] drm/panel: simple: restore connector_type fallback
> config: arm-randconfig-002-20251123 (https://download.01.org/0day-ci/archive/20251123/202511230354.nHRvfjDz-lkp@intel.com/config)
> compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 9e9fe08b16ea2c4d9867fb4974edf2a3776d6ece)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251123/202511230354.nHRvfjDz-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202511230354.nHRvfjDz-lkp@intel.com/
>
> All warnings (new ones prefixed by >>):
>
>>> drivers/gpu/drm/panel/panel-simple.c:648:7: warning: variable 'panel' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
> 648 | case DRM_MODE_CONNECTOR_eDP:
> | ^~~~~~~~~~~~~~~~~~~~~~
> include/uapi/drm/drm_mode.h:417:33: note: expanded from macro 'DRM_MODE_CONNECTOR_eDP'
> 417 | #define DRM_MODE_CONNECTOR_eDP 14
> | ^~
> drivers/gpu/drm/panel/panel-simple.c:749:6: note: uninitialized use occurs here
> 749 | if (panel->ddc)
> | ^~~~~
> drivers/gpu/drm/panel/panel-simple.c:615:28: note: initialize the variable 'panel' to silence this warning
> 615 | struct panel_simple *panel;
> | ^
> | = NULL
> 1 warning generated.
>
>
> vim +/panel +648 drivers/gpu/drm/panel/panel-simple.c
>
> 47c08262f34e1c Maxime Ripard 2025-06-26 611
> 47c08262f34e1c Maxime Ripard 2025-06-26 612 static struct panel_simple *panel_simple_probe(struct device *dev)
> 280921de7241ee Thierry Reding 2013-08-30 613 {
> 47c08262f34e1c Maxime Ripard 2025-06-26 614 const struct panel_desc *desc;
> 280921de7241ee Thierry Reding 2013-08-30 615 struct panel_simple *panel;
> b8a2948fa2b3a5 Sean Paul 2019-07-11 616 struct display_timing dt;
> 0fe1564bd61642 Sam Ravnborg 2019-12-07 617 struct device_node *ddc;
> 9f069c6fbc7266 Sam Ravnborg 2020-07-26 618 int connector_type;
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 619 u32 bus_flags;
> 280921de7241ee Thierry Reding 2013-08-30 620 int err;
> 280921de7241ee Thierry Reding 2013-08-30 621
> 47c08262f34e1c Maxime Ripard 2025-06-26 622 desc = panel_simple_get_desc(dev);
> 47c08262f34e1c Maxime Ripard 2025-06-26 623 if (IS_ERR(desc))
> 47c08262f34e1c Maxime Ripard 2025-06-26 624 return ERR_CAST(desc);
> 47c08262f34e1c Maxime Ripard 2025-06-26 625
> 9f069c6fbc7266 Sam Ravnborg 2020-07-26 626 connector_type = desc->connector_type;
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 627 /* Catch common mistakes for panels. */
> 9f069c6fbc7266 Sam Ravnborg 2020-07-26 628 switch (connector_type) {
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 629 case 0:
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 630 dev_warn(dev, "Specify missing connector_type\n");
> 9f069c6fbc7266 Sam Ravnborg 2020-07-26 631 connector_type = DRM_MODE_CONNECTOR_DPI;
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 632 break;
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 633 case DRM_MODE_CONNECTOR_LVDS:
> c4715837b02393 Laurent Pinchart 2020-06-30 634 WARN_ON(desc->bus_flags &
> c4715837b02393 Laurent Pinchart 2020-06-30 635 ~(DRM_BUS_FLAG_DE_LOW |
> c4715837b02393 Laurent Pinchart 2020-06-30 636 DRM_BUS_FLAG_DE_HIGH |
> c4715837b02393 Laurent Pinchart 2020-06-30 637 DRM_BUS_FLAG_DATA_MSB_TO_LSB |
> c4715837b02393 Laurent Pinchart 2020-06-30 638 DRM_BUS_FLAG_DATA_LSB_TO_MSB));
> 1185c406f11a49 Laurent Pinchart 2020-06-30 639 WARN_ON(desc->bus_format != MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
> 1185c406f11a49 Laurent Pinchart 2020-06-30 640 desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_SPWG &&
> 1185c406f11a49 Laurent Pinchart 2020-06-30 641 desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA);
> 1185c406f11a49 Laurent Pinchart 2020-06-30 642 WARN_ON(desc->bus_format == MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
> 1185c406f11a49 Laurent Pinchart 2020-06-30 643 desc->bpc != 6);
> 1185c406f11a49 Laurent Pinchart 2020-06-30 644 WARN_ON((desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_SPWG ||
> 1185c406f11a49 Laurent Pinchart 2020-06-30 645 desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA) &&
> 1185c406f11a49 Laurent Pinchart 2020-06-30 646 desc->bpc != 8);
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 647 break;
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 @648 case DRM_MODE_CONNECTOR_eDP:
> 5f04e7ce392db9 Douglas Anderson 2021-09-14 649 dev_warn(dev, "eDP panels moved to panel-edp\n");
> 5f04e7ce392db9 Douglas Anderson 2021-09-14 650 err = -EINVAL;
> 5f04e7ce392db9 Douglas Anderson 2021-09-14 651 goto free_ddc;
The error is legitimate, here we'll try to access panel->ddc, but the panel isn't allocated.
Please fix this.
Neil
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 652 case DRM_MODE_CONNECTOR_DSI:
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 653 if (desc->bpc != 6 && desc->bpc != 8)
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 654 dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 655 break;
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 656 case DRM_MODE_CONNECTOR_DPI:
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 657 bus_flags = DRM_BUS_FLAG_DE_LOW |
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 658 DRM_BUS_FLAG_DE_HIGH |
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 659 DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE |
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 660 DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE |
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 661 DRM_BUS_FLAG_DATA_MSB_TO_LSB |
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 662 DRM_BUS_FLAG_DATA_LSB_TO_MSB |
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 663 DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE |
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 664 DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE;
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 665 if (desc->bus_flags & ~bus_flags)
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 666 dev_warn(dev, "Unexpected bus_flags(%d)\n", desc->bus_flags & ~bus_flags);
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 667 if (!(desc->bus_flags & bus_flags))
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 668 dev_warn(dev, "Specify missing bus_flags\n");
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 669 if (desc->bus_format == 0)
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 670 dev_warn(dev, "Specify missing bus_format\n");
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 671 if (desc->bpc != 6 && desc->bpc != 8)
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 672 dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 673 break;
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 674 default:
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 675 dev_warn(dev, "Specify a valid connector_type: %d\n", desc->connector_type);
> 9f069c6fbc7266 Sam Ravnborg 2020-07-26 676 connector_type = DRM_MODE_CONNECTOR_DPI;
> ddb8e853dc8507 Sam Ravnborg 2020-07-26 677 break;
> 1185c406f11a49 Laurent Pinchart 2020-06-30 678 }
> c4715837b02393 Laurent Pinchart 2020-06-30 679
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 680 panel = devm_drm_panel_alloc(dev, struct panel_simple, base,
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 681 &panel_simple_funcs, connector_type);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 682 if (IS_ERR(panel))
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 683 return ERR_CAST(panel);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 684
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 685 panel->desc = desc;
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 686
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 687 panel->supply = devm_regulator_get(dev, "power");
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 688 if (IS_ERR(panel->supply))
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 689 return ERR_CAST(panel->supply);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 690
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 691 panel->enable_gpio = devm_gpiod_get_optional(dev, "enable",
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 692 GPIOD_OUT_LOW);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 693 if (IS_ERR(panel->enable_gpio))
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 694 return dev_err_cast_probe(dev, panel->enable_gpio,
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 695 "failed to request GPIO\n");
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 696
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 697 err = of_drm_get_panel_orientation(dev->of_node, &panel->orientation);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 698 if (err) {
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 699 dev_err(dev, "%pOF: failed to get orientation %d\n", dev->of_node, err);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 700 return ERR_PTR(err);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 701 }
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 702
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 703 ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 704 if (ddc) {
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 705 panel->ddc = of_find_i2c_adapter_by_node(ddc);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 706 of_node_put(ddc);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 707
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 708 if (!panel->ddc)
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 709 return ERR_PTR(-EPROBE_DEFER);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 710 }
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 711
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 712 if (!of_device_is_compatible(dev->of_node, "panel-dpi") &&
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 713 !of_get_display_timing(dev->of_node, "panel-timing", &dt))
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 714 panel_simple_parse_panel_timing_node(dev, panel, &dt);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 715
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 716 if (desc->connector_type == DRM_MODE_CONNECTOR_LVDS) {
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 717 /* Optional data-mapping property for overriding bus format */
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 718 err = panel_simple_override_nondefault_lvds_datamapping(dev, panel);
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 719 if (err)
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 720 goto free_ddc;
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 721 }
> 2803eb4aeb2702 Ludovic Desroches 2025-11-21 722
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 723 dev_set_drvdata(dev, panel);
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 724
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 725 /*
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 726 * We use runtime PM for prepare / unprepare since those power the panel
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 727 * on and off and those can be very slow operations. This is important
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 728 * to optimize powering the panel on briefly to read the EDID before
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 729 * fully enabling the panel.
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 730 */
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 731 pm_runtime_enable(dev);
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 732 pm_runtime_set_autosuspend_delay(dev, 1000);
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 733 pm_runtime_use_autosuspend(dev);
> 3235b0f20a0a41 Douglas Anderson 2021-04-16 734
> 0fe1564bd61642 Sam Ravnborg 2019-12-07 735 err = drm_panel_of_backlight(&panel->base);
> d9e74da2f1fc42 Alexander Stein 2022-06-21 736 if (err) {
> d9e74da2f1fc42 Alexander Stein 2022-06-21 737 dev_err_probe(dev, err, "Could not find backlight\n");
> 70e12560126685 Douglas Anderson 2021-04-23 738 goto disable_pm_runtime;
> d9e74da2f1fc42 Alexander Stein 2022-06-21 739 }
> 0fe1564bd61642 Sam Ravnborg 2019-12-07 740
> c3ee8c65f63799 Bernard Zhao 2020-08-01 741 drm_panel_add(&panel->base);
> 280921de7241ee Thierry Reding 2013-08-30 742
> 921c41e509746a Maxime Ripard 2025-06-26 743 return panel;
> 280921de7241ee Thierry Reding 2013-08-30 744
> 70e12560126685 Douglas Anderson 2021-04-23 745 disable_pm_runtime:
> a596fcd9cbc781 Douglas Anderson 2021-05-17 746 pm_runtime_dont_use_autosuspend(dev);
> 70e12560126685 Douglas Anderson 2021-04-23 747 pm_runtime_disable(dev);
> 280921de7241ee Thierry Reding 2013-08-30 748 free_ddc:
> 5f04e7ce392db9 Douglas Anderson 2021-09-14 749 if (panel->ddc)
> 280921de7241ee Thierry Reding 2013-08-30 750 put_device(&panel->ddc->dev);
> 280921de7241ee Thierry Reding 2013-08-30 751
> 921c41e509746a Maxime Ripard 2025-06-26 752 return ERR_PTR(err);
> 280921de7241ee Thierry Reding 2013-08-30 753 }
> 280921de7241ee Thierry Reding 2013-08-30 754
>
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