linux-kernel - [bug report] drm/amd/display: Only poll analog connectors

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Message-ID: <aYXva0vNgvjdwvk2@stanley.mountain>
Date: Fri, 6 Feb 2026 16:40:59 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Timur Kristóf <timur.kristof@...il.com>
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	"SHANMUGAM, SRINIVASAN" <SRINIVASAN.SHANMUGAM@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [bug report] drm/amd/display: Only poll analog connectors

[ Smatch checking is paused while we raise funding.  #SadFace
  https://lore.kernel.org/all/aTaiGSbWZ9DJaGo7@stanley.mountain/ -dan ]

Hello Timur Kristóf,

Commit f6cc7f1c11a7 ("drm/amd/display: Only poll analog connectors")
from Jan 18, 2026 (linux-next), leads to the following Smatch static
checker warning:

	drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_irq.c:940 amdgpu_dm_hpd_init()
	error: we previously assumed 'dc_link' could be null (see line 931)

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_irq.c
    923                 /*
    924                  * Analog connectors may be hot-plugged unlike other connector
    925                  * types that don't support HPD. Only poll analog connectors.
    926                  */
    927                 use_polling |=
    928                         amdgpu_dm_connector->dc_link &&
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The patch adds this NULL check but hopefully it can be removed

    929                         dc_connector_supports_analog(amdgpu_dm_connector->dc_link->link_id.id);
    930 
    931                 dc_link = amdgpu_dm_connector->dc_link;

dc_link assigned here.

    932 
    933                 /*
    934                  * Get a base driver irq reference for hpd ints for the lifetime
    935                  * of dm. Note that only hpd interrupt types are registered with
    936                  * base driver; hpd_rx types aren't. IOW, amdgpu_irq_get/put on
    937                  * hpd_rx isn't available. DM currently controls hpd_rx
    938                  * explicitly with dc_interrupt_set()
    939                  */
--> 940                 if (dc_link->irq_source_hpd != DC_IRQ_SOURCE_INVALID) {
                            ^^^^^^^^^^^^^^^^^^^^^^^
If it's NULL then we are trouble because we dereference it here.

    941                         irq_type = dc_link->irq_source_hpd - DC_IRQ_SOURCE_HPD1;
    942                         /*
    943                          * TODO: There's a mismatch between mode_info.num_hpd
    944                          * and what bios reports as the # of connectors with hpd

regards,
dan carpenter