Messages in this thread | | | Subject | Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj' | From | Randy Dunlap <> | Date | Tue, 26 Oct 2021 23:26:07 -0700 |
| |
On 10/26/21 11:19 PM, Arnd Bergmann wrote: > On Wed, Oct 27, 2021 at 2:58 AM Randy Dunlap <rdunlap@infradead.org> wrote: > >>> >>> Looking at this config, there is: >>> >>> CONFIG_DRM=y >>> # CONFIG_DRM_DP_AUX_CHARDEV is not set >>> # CONFIG_DRM_DEBUG_MM is not set >>> # CONFIG_DRM_DEBUG_SELFTEST is not set >>> CONFIG_DRM_KMS_HELPER=m >>> # CONFIG_DRM_LOAD_EDID_FIRMWARE is not set >>> # CONFIG_DRM_DP_CEC is not set >>> CONFIG_DRM_GEM_CMA_HELPER=y >>> CONFIG_DRM_KMS_CMA_HELPER=y >>> >>> GEM_CMA_HELPER depends on KMS_HELPER, but the latter is a module. That's probably the cause of the problem. Is it intentionally set this way? >>> >> >> The only drivers that select DRM_KMS_HELPER are both =m, so that's how >> DRM_KMS_HELPER is set also. >> >> Symbol: DRM_KMS_HELPER [=m] >> Type : tristate >> Defined at drivers/gpu/drm/Kconfig:82 >> Depends on: HAS_IOMEM [=y] && DRM [=y] >> Selected by [m]: >> - DRM_ATMEL_HLCDC [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && COMMON_CLK [=y] && MFD_ATMEL_HLCDC [=y] && ARM [=y] >> - DRM_ASPEED_GFX [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && (COMPILE_TEST [=n] || ARCH_ASPEED [=y]) && MMU [=y] >> >> >> I did the ARM cross-build and also see the linker error. >> I didn't understand why -- and still don't, but here is a little >> speculation: >> >> In the past (e.g. 10 years ago), we have to move some .o files >> in lib/ from lib-y to obj-y so that they would always be included >> in the final object file and not cause their user/caller object >> files to suffer from undefined references. >> These happened because unused functions(?) in lib-y files are >> stripped out of the final object files. >> The same thing could be happening here (still just guessing). >> >> Does that help any? I dunno. >> >> Adding Arnd to Cc: to see if he has any ideas... > > From all I can tell, the problem is that DRM_KMS_CMA_HELPER is a 'bool' > symbol, so if it gets selected by a '=m' driver, it turns into '=y', which > then selects DRM_GEM_CMA_HELPER=y, but that one cannot link > against DRM_KMS_HELPER=m code. > > This trivial change makes it all build: > > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig > index c08860db2520..699f434ce813 100644 > --- a/drivers/gpu/drm/Kconfig > +++ b/drivers/gpu/drm/Kconfig > @@ -218,7 +218,7 @@ config DRM_GEM_CMA_HELPER > Choose this if you need the GEM CMA helper functions > > config DRM_KMS_CMA_HELPER > - bool > + tristate > depends on DRM > select DRM_GEM_CMA_HELPER > help > > but this needs some more testing to make sure it doesn't add > any other regressions. > > Interestingly, I never hit the problem in randconfig testing since > there is always some '=y' driver that selects DRM_KMS_HELPER. > > Arnd >
Hi Arnd, Thomas had posted a patch that also fixes the problem. Somehow I missed seeing that the first time around.
Thanks. -- ~Randy
| |