Re: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper

Re: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper

[Gary Chu(楚光庆)]

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Hi Thomas

This is what I've done in the yhgch_drm driver.
See the link below:
https://lore.kernel.org/all/20250808053508.52202-1-chuguangqing@inspur.com/T/#t

In fact, through modifications in Patch v2, it allows only the selection of 
DRM_VRAM_HELPER in the driver.
See the link below:
https://lore.kernel.org/all/20250729060728.82402-1-chuguangqing@inspur.com/T/#m3e33f8e155275ea548223c21777c191ecd392159

Best regards
Chuguangqing

> From: Thomas Zimmermann <tzimmermann@suse.de>
> To:chuguangqing <chuguangqing@inspur.com>; Maarten Lankhorst
> <maarten.lankhorst@linux.intel.com>; Maxime Ripard <mripard@kernel.org>;
> David Airlie <airlied@gmail.com>; Simona Vetter <simona@ffwll.ch>
> Cc: dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper
>
> Hi
>
> Am 29.07.25 um 08:07 schrieb chuguangqing:
> > We encountered the following errors while compiling drm_vram_helper.ko
> >
> > ERROR: modpost: "drm_gem_ttm_print_info"
> [drivers/gpu/drm/drm_vram_helper.ko] undefined!
> > ERROR: modpost: "drm_gem_ttm_mmap"
> [drivers/gpu/drm/drm_vram_helper.ko] undefined!
> >
> > The functions drm_gem_ttm_mmap and drm_gem_ttm_print_info are
> defined in drm_gem_ttm_helper.c. This patch adds drm_gem_ttm_helper.o to
> DRM_VRAM_HELPER to resolve the undefined symbol errors.
>
> You need to select DRM_TTM_HELPER for your driver.
>
> Best regards
> Thomas
>
> >
> > Signed-off-by: chuguangqing <chuguangqing@inspur.com>
> > ---
> >   drivers/gpu/drm/Makefile | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile index
> > 4dafbdc8f86a..abbe32ddf6d0 100644
> > --- a/drivers/gpu/drm/Makefile
> > +++ b/drivers/gpu/drm/Makefile
> > @@ -125,7 +125,7 @@ drm_suballoc_helper-y := drm_suballoc.o
> >   obj-$(CONFIG_DRM_SUBALLOC_HELPER) += drm_suballoc_helper.o
> >
> >   drm_vram_helper-y := drm_gem_vram_helper.o
> > -obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
> > +obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
> > +drm_gem_ttm_helper.o
> >
> >   drm_ttm_helper-y := drm_gem_ttm_helper.o
> >   drm_ttm_helper-$(CONFIG_DRM_FBDEV_EMULATION) +=
> drm_fbdev_ttm.o
>
> --
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Frankenstrasse 146, 90461 Nuernberg, Germany
> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB
> 36809 (AG Nuernberg)
>


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Re: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper

[Thomas Zimmermann]

Hi

Am 13.08.25 um 03:38 schrieb Gary Chu(楚光庆):
> Hi Thomas
>
> This is what I've done in the yhgch_drm driver.
> See the link below:
> https://lore.kernel.org/all/20250808053508.52202-1-chuguangqing@inspur.com/T/#t

I see. I thought it was for an existing driver. In new drivers, please 
don't use VRAM helpers any longer. VRAM helpers are based on TTM and new 
drivers should use TTM directly. If you integrate the code from VRAM 
helpers into your driver, you should be good.

Note that for reliably using TTM, your hardware requires at least 3 
times the memory as the largest resolution+depth requires. The driver 
says 1920*1200@32bpp, which amounts to ~9 MiB of VRAM. For TTM usage, 
your device requires at least 32 MiB of VRAM available.

If your devices have smaller VRAM, rather use GEM SHMEM helpers instead.

Best regards
Thomas

>
> In fact, through modifications in Patch v2, it allows only the selection of
> DRM_VRAM_HELPER in the driver.
> See the link below:
> https://lore.kernel.org/all/20250729060728.82402-1-chuguangqing@inspur.com/T/#m3e33f8e155275ea548223c21777c191ecd392159
>
> Best regards
> Chuguangqing
>
>> From: Thomas Zimmermann <tzimmermann@suse.de>
>> To:chuguangqing <chuguangqing@inspur.com>; Maarten Lankhorst
>> <maarten.lankhorst@linux.intel.com>; Maxime Ripard <mripard@kernel.org>;
>> David Airlie <airlied@gmail.com>; Simona Vetter <simona@ffwll.ch>
>> Cc: dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org
>> Subject: Re: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper
>>
>> Hi
>>
>> Am 29.07.25 um 08:07 schrieb chuguangqing:
>>> We encountered the following errors while compiling drm_vram_helper.ko
>>>
>>> ERROR: modpost: "drm_gem_ttm_print_info"
>> [drivers/gpu/drm/drm_vram_helper.ko] undefined!
>>> ERROR: modpost: "drm_gem_ttm_mmap"
>> [drivers/gpu/drm/drm_vram_helper.ko] undefined!
>>> The functions drm_gem_ttm_mmap and drm_gem_ttm_print_info are
>> defined in drm_gem_ttm_helper.c. This patch adds drm_gem_ttm_helper.o to
>> DRM_VRAM_HELPER to resolve the undefined symbol errors.
>>
>> You need to select DRM_TTM_HELPER for your driver.
>>
>> Best regards
>> Thomas
>>
>>> Signed-off-by: chuguangqing <chuguangqing@inspur.com>
>>> ---
>>>    drivers/gpu/drm/Makefile | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile index
>>> 4dafbdc8f86a..abbe32ddf6d0 100644
>>> --- a/drivers/gpu/drm/Makefile
>>> +++ b/drivers/gpu/drm/Makefile
>>> @@ -125,7 +125,7 @@ drm_suballoc_helper-y := drm_suballoc.o
>>>    obj-$(CONFIG_DRM_SUBALLOC_HELPER) += drm_suballoc_helper.o
>>>
>>>    drm_vram_helper-y := drm_gem_vram_helper.o
>>> -obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
>>> +obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
>>> +drm_gem_ttm_helper.o
>>>
>>>    drm_ttm_helper-y := drm_gem_ttm_helper.o
>>>    drm_ttm_helper-$(CONFIG_DRM_FBDEV_EMULATION) +=
>> drm_fbdev_ttm.o
>>
>> --
>> --
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Frankenstrasse 146, 90461 Nuernberg, Germany
>> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB
>> 36809 (AG Nuernberg)
>>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

Re: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper

[Thomas Zimmermann]

Hi

Am 13.08.25 um 08:58 schrieb Thomas Zimmermann:
> Hi
>
> Am 13.08.25 um 03:38 schrieb Gary Chu(楚光庆):
>> Hi Thomas
>>
>> This is what I've done in the yhgch_drm driver.
>> See the link below:
>> https://lore.kernel.org/all/20250808053508.52202-1-chuguangqing@inspur.com/T/#t 
>>
>
> I see. I thought it was for an existing driver. In new drivers, please 
> don't use VRAM helpers any longer. VRAM helpers are based on TTM and 
> new drivers should use TTM directly. If you integrate the code from 
> VRAM helpers into your driver, you should be good.
>
> Note that for reliably using TTM, your hardware requires at least 3 
> times the memory as the largest resolution+depth requires. The driver 
> says 1920*1200@32bpp, which amounts to ~9 MiB of VRAM. For TTM usage, 
> your device requires at least 32 MiB of VRAM available.
>
> If your devices have smaller VRAM, rather use GEM SHMEM helpers instead.

And with TTM, buffer sharing is fairly hard to impossible. Shmem or DMA 
helpers provide it out of the box.

Best regards
Thomas


>
> Best regards
> Thomas
>
>>
>> In fact, through modifications in Patch v2, it allows only the 
>> selection of
>> DRM_VRAM_HELPER in the driver.
>> See the link below:
>> https://lore.kernel.org/all/20250729060728.82402-1-chuguangqing@inspur.com/T/#m3e33f8e155275ea548223c21777c191ecd392159 
>>
>>
>> Best regards
>> Chuguangqing
>>
>>> From: Thomas Zimmermann <tzimmermann@suse.de>
>>> To:chuguangqing <chuguangqing@inspur.com>; Maarten Lankhorst
>>> <maarten.lankhorst@linux.intel.com>; Maxime Ripard 
>>> <mripard@kernel.org>;
>>> David Airlie <airlied@gmail.com>; Simona Vetter <simona@ffwll.ch>
>>> Cc: dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org
>>> Subject: Re: [PATCH 1/1] gpu: drm: fix compilation errors in 
>>> drm_vram_helper
>>>
>>> Hi
>>>
>>> Am 29.07.25 um 08:07 schrieb chuguangqing:
>>>> We encountered the following errors while compiling drm_vram_helper.ko
>>>>
>>>> ERROR: modpost: "drm_gem_ttm_print_info"
>>> [drivers/gpu/drm/drm_vram_helper.ko] undefined!
>>>> ERROR: modpost: "drm_gem_ttm_mmap"
>>> [drivers/gpu/drm/drm_vram_helper.ko] undefined!
>>>> The functions drm_gem_ttm_mmap and drm_gem_ttm_print_info are
>>> defined in drm_gem_ttm_helper.c. This patch adds 
>>> drm_gem_ttm_helper.o to
>>> DRM_VRAM_HELPER to resolve the undefined symbol errors.
>>>
>>> You need to select DRM_TTM_HELPER for your driver.
>>>
>>> Best regards
>>> Thomas
>>>
>>>> Signed-off-by: chuguangqing <chuguangqing@inspur.com>
>>>> ---
>>>>    drivers/gpu/drm/Makefile | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile index
>>>> 4dafbdc8f86a..abbe32ddf6d0 100644
>>>> --- a/drivers/gpu/drm/Makefile
>>>> +++ b/drivers/gpu/drm/Makefile
>>>> @@ -125,7 +125,7 @@ drm_suballoc_helper-y := drm_suballoc.o
>>>>    obj-$(CONFIG_DRM_SUBALLOC_HELPER) += drm_suballoc_helper.o
>>>>
>>>>    drm_vram_helper-y := drm_gem_vram_helper.o
>>>> -obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
>>>> +obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
>>>> +drm_gem_ttm_helper.o
>>>>
>>>>    drm_ttm_helper-y := drm_gem_ttm_helper.o
>>>>    drm_ttm_helper-$(CONFIG_DRM_FBDEV_EMULATION) +=
>>> drm_fbdev_ttm.o
>>>
>>> -- 
>>> -- 
>>> Thomas Zimmermann
>>> Graphics Driver Developer
>>> SUSE Software Solutions Germany GmbH
>>> Frankenstrasse 146, 90461 Nuernberg, Germany
>>> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB
>>> 36809 (AG Nuernberg)
>>>
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

Re: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper

[chuguangqing]

I see. This compilation error was caused by the configuration option not automatically selecting DRM_TTM_HELPER. A revised version of the PR has been submitted.

[PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper

[chuguangqing]

We encountered the following errors while compiling drm_vram_helper.ko

ERROR: modpost: "drm_gem_ttm_print_info" [drivers/gpu/drm/drm_vram_helper.ko] undefined!
ERROR: modpost: "drm_gem_ttm_mmap" [drivers/gpu/drm/drm_vram_helper.ko] undefined!

The functions drm_gem_ttm_mmap and drm_gem_ttm_print_info are defined in drm_gem_ttm_helper.c. This patch adds drm_gem_ttm_helper.o to DRM_VRAM_HELPER to resolve the undefined symbol errors.

Signed-off-by: chuguangqing <chuguangqing@inspur.com>
---
 drivers/gpu/drm/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 4dafbdc8f86a..abbe32ddf6d0 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -125,7 +125,7 @@ drm_suballoc_helper-y := drm_suballoc.o
 obj-$(CONFIG_DRM_SUBALLOC_HELPER) += drm_suballoc_helper.o
 
 drm_vram_helper-y := drm_gem_vram_helper.o
-obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
+obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o drm_gem_ttm_helper.o
 
 drm_ttm_helper-y := drm_gem_ttm_helper.o
 drm_ttm_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fbdev_ttm.o
-- 
2.43.5

Re: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper

[kernel test robot]

Hi chuguangqing,

kernel test robot noticed the following build errors:

[auto build test ERROR on linus/master]
[also build test ERROR on drm-misc/drm-misc-next v6.16 next-20250729]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/chuguangqing/gpu-drm-fix-compilation-errors-in-drm_vram_helper/20250729-141222
base:   linus/master
patch link:    https://lore.kernel.org/r/20250729060728.82402-1-chuguangqing%40inspur.com
patch subject: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper
:::::: branch date: 16 hours ago
:::::: commit date: 16 hours ago
config: s390-randconfig-001-20250730 (https://download.01.org/0day-ci/archive/20250730/202507300646.kTchyjvh-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250730/202507300646.kTchyjvh-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@intel.com>
| Closes: https://lore.kernel.org/r/202507300646.kTchyjvh-lkp@intel.com/

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: drivers/gpu/drm/drm_gem_ttm_helper: 'drm_gem_ttm_print_info' exported twice. Previous export was in vmlinux
>> ERROR: modpost: drivers/gpu/drm/drm_gem_ttm_helper: 'drm_gem_ttm_vmap' exported twice. Previous export was in vmlinux
>> ERROR: modpost: drivers/gpu/drm/drm_gem_ttm_helper: 'drm_gem_ttm_vunmap' exported twice. Previous export was in vmlinux
>> ERROR: modpost: drivers/gpu/drm/drm_gem_ttm_helper: 'drm_gem_ttm_mmap' exported twice. Previous export was in vmlinux
>> ERROR: modpost: drivers/gpu/drm/drm_gem_ttm_helper: 'drm_gem_ttm_dumb_map_offset' exported twice. Previous export was in vmlinux

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 1/1] gpu: drm: fix compilation errors in drm_vram_helper

[Thomas Zimmermann]

Hi

Am 29.07.25 um 08:07 schrieb chuguangqing:
> We encountered the following errors while compiling drm_vram_helper.ko
>
> ERROR: modpost: "drm_gem_ttm_print_info" [drivers/gpu/drm/drm_vram_helper.ko] undefined!
> ERROR: modpost: "drm_gem_ttm_mmap" [drivers/gpu/drm/drm_vram_helper.ko] undefined!
>
> The functions drm_gem_ttm_mmap and drm_gem_ttm_print_info are defined in drm_gem_ttm_helper.c. This patch adds drm_gem_ttm_helper.o to DRM_VRAM_HELPER to resolve the undefined symbol errors.

You need to select DRM_TTM_HELPER for your driver.

Best regards
Thomas

>
> Signed-off-by: chuguangqing <chuguangqing@inspur.com>
> ---
>   drivers/gpu/drm/Makefile | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 4dafbdc8f86a..abbe32ddf6d0 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -125,7 +125,7 @@ drm_suballoc_helper-y := drm_suballoc.o
>   obj-$(CONFIG_DRM_SUBALLOC_HELPER) += drm_suballoc_helper.o
>   
>   drm_vram_helper-y := drm_gem_vram_helper.o
> -obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
> +obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o drm_gem_ttm_helper.o
>   
>   drm_ttm_helper-y := drm_gem_ttm_helper.o
>   drm_ttm_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fbdev_ttm.o

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)