Re: [PATCH v2] soc: qcom: ubwc: Fix link error when QCOM_SMEM=n

[Nathan Chancellor <nathan@kernel.org>]

On Tue, Aug 11, 2026 at 06:19:05PM +0300, Daniel Baluta wrote:
> DRM_MSM unconditionally selects QCOM_UBWC_CONFIG, which calls SMEM APIs,
> causing a link error on non-Qcom platforms (e.g. SOC_IMX5):
> 
>   arm-linux-gnueabihf-ld: ubwc_config.c:(.text+0x2c): undefined
>       reference to 'qcom_smem_is_available'
>   arm-linux-gnueabihf-ld: ubwc_config.c:(.text+0x4c): undefined
>       reference to 'qcom_smem_dram_get_hbb'
> 
> Relax the selection of QCOM_UBWC_CONFIG to ARCH_QCOM only and make QCOM_UBWC_CONFIG
> depend on QCOM_SMEM make the requirement explicit.
> 
> Fixes: 1b445022d1d0 ("soc: qcom: ubwc: Get HBB from SMEM")
> Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
> ---
> Changes since v1:
> - (addressed feedback from Dmitry) replace adding static inline stubs with preparing a better config
>   dependecies so that we use the qcom_smem symbols only on QCOM platforms.
> - Link to v1: https://lore.kernel.org/imx/sy2ulk536ryakhy6fdnqr4asvzvufqk3dlo2awdrfomulyf4n4@qtp4qoazqmhj/T/#t
> 
>  drivers/gpu/drm/msm/Kconfig | 2 +-
>  drivers/soc/qcom/Kconfig    | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/Kconfig b/drivers/gpu/drm/msm/Kconfig
> index 09469d56513b0..ab3844521255e 100644
> --- a/drivers/gpu/drm/msm/Kconfig
> +++ b/drivers/gpu/drm/msm/Kconfig
> @@ -22,7 +22,7 @@ config DRM_MSM
>  	select TMPFS
>  	select QCOM_SCM
>  	select QCOM_PAS
> -	select QCOM_UBWC_CONFIG
> +	select QCOM_UBWC_CONFIG if ARCH_QCOM
>  	select WANT_DEV_COREDUMP
>  	select SND_SOC_HDMI_CODEC if SND_SOC
>  	select SYNC_FILE
> diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
> index fd4d4ecd2df0f..e0629e9328c87 100644
> --- a/drivers/soc/qcom/Kconfig
> +++ b/drivers/soc/qcom/Kconfig
> @@ -321,6 +321,7 @@ config QCOM_QMI_HELPERS
>  
>  config QCOM_UBWC_CONFIG
>  	tristate
> +	depends on QCOM_SMEM
>  	help
>  	  Most Qualcomm SoCs feature a number of Universal Bandwidth Compression
>  	  (UBWC) engines across various IP blocks, which need to be initialized
> -- 
> 2.45.2
> 

This does not fully fix the issue. ARCH_QCOM=y and QCOM_SMEM=n will
still trigger the issue because select does not respect dependencies:

  $ echo CONFIG_QCOM_SMEM=n >kernel/configs/no_smem.config

  $ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- mrproper defconfig no_smem.config all
  WARNING: unmet direct dependencies detected for QCOM_UBWC_CONFIG
    Depends on [n]: QCOM_SMEM [=n]
    Selected by [m]:
    - DRM_MSM [=m] && HAS_IOMEM [=y] && DRM [=y] && (ARCH_QCOM [=y] || SOC_IMX5 [=y] || COMPILE_TEST [=n]) && COMMON_CLK [=y] && IOMMU_SUPPORT [=y] && OF [=y] && (QCOM_AOSS_QMP [=y] || QCOM_AOSS_QMP [=y]=n [=n]) && (QCOM_OCMEM [=m] || QCOM_OCMEM [=m]=n [=n]) && (QCOM_LLCC [=m] || QCOM_LLCC [=m]=n [=n]) && (QCOM_COMMAND_DB [=m] || QCOM_COMMAND_DB [=m]=n [=n]) && PM [=y] && ARCH_QCOM [=y]
  ERROR: modpost: drivers/soc/qcom/ubwc_config.ko: symbol 'qcom_smem_is_available' undefined!
  ERROR: modpost: drivers/soc/qcom/ubwc_config.ko: symbol 'qcom_smem_dram_get_hbb' undefined!
  ...

-- 
Cheers,
Nathan