Hi,
On Mon, Aug 15, 2022 at 12:09 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
From: Gao Chao gaochao49@huawei.com
[ Upstream commit a67664860f7833015a683ea295f7c79ac2901332 ]
If CONFIG_DRM_PANEL_SAMSUNG_ATNA33XC20=y && CONFIG_DRM_DISPLAY_HELPER=m, bulding fails:
drivers/gpu/drm/panel/panel-samsung-atna33xc20.o: In function `atana33xc20_probe': panel-samsung-atna33xc20.c:(.text+0x744): undefined reference to `drm_panel_dp_aux_backlight' make: *** [vmlinux] Error 1
Let CONFIG_DRM_PANEL_SAMSUNG_ATNA33XC20 select DRM_DISPLAY_DP_HELPER and CONFIG_DRM_DISPLAY_HELPER to fix this error.
Fixes: 32ce3b320343 ("drm/panel: atna33xc20: Introduce the Samsung ATNA33XC20 panel") Reported-by: Hulk Robot hulkci@huawei.com Signed-off-by: Gao Chao gaochao49@huawei.com Reviewed-by: Douglas Anderson dianders@chromium.org Signed-off-by: Douglas Anderson dianders@chromium.org Link: https://patchwork.freedesktop.org/patch/msgid/20220524024551.539-1-gaochao49... Signed-off-by: Sasha Levin sashal@kernel.org
drivers/gpu/drm/panel/Kconfig | 2 ++ 1 file changed, 2 insertions(+)
While it doesn't hurt to land this patch as-is on 5.18 and older kernels, it's not quite right. The symbols that this patch 'select' don't actually exist on 5.18. ;-) Doing a `git grep` of `DRM_DISPLAY_DP_HELPER` shows no hits except the one introduced in this patch...
If you want the equivalent fix for v5.18 and older, I believe you'd want:
select DRM_DP_HELPER select DRM_KMS_HELPER
See commit 3755d35ee1d2 ("drm/panel: Select DRM_DP_HELPER for DRM_PANEL_EDP") and commit 3c3384050d68 ("drm: Don't make DRM_PANEL_BRIDGE dependent on DRM_KMS_HELPERS") which added those for the (very similar) panel-edp.
The first of those is what got changed in v5.19 in commit 1e0f66420b13 ("drm/display: Introduce a DRM display-helper module")
So I guess the tl;dr:
* If you leave this patch in 5.18 (and 5.15), nothing bad will happen but the broken "randconfig" won't be fixed.
* If you revert this patch in 5.18 (and 5.15) also nothing bad will happen but also the broken "randconfig" won't be fixed.
* If someone cares about the randconfig on 5.15 / 5.18, we need a backport that adapts what's selected to the old symbol names.