[PATCH v2 1/3] fbdev: Fix recursive dependencies wrt BACKLIGHT_CLASS_DEVICE

[Christophe Leroy]

Le 13/12/2024 à 09:05, Thomas Zimmermann a écrit :
> Hi
> 
> 
> Am 13.12.24 um 08:44 schrieb Christophe Leroy:
>>
>>
>> Le 12/12/2024 à 11:04, Thomas Zimmermann a écrit :
>>> Do not select BACKLIGHT_CLASS_DEVICE from FB_BACKLIGHT. The latter
>>> only controls backlight support within fbdev core code and data
>>> structures.
>>>
>>> Make fbdev drivers depend on BACKLIGHT_CLASS_DEVICE and let users
>>> select it explicitly. Fixes warnings about recursive dependencies,
>>> such as
>>>
>>> error: recursive dependency detected!
>>>     symbol BACKLIGHT_CLASS_DEVICE is selected by FB_BACKLIGHT
>>>     symbol FB_BACKLIGHT is selected by FB_SH_MOBILE_LCDC
>>>     symbol FB_SH_MOBILE_LCDC depends on FB_DEVICE
>>>     symbol FB_DEVICE depends on FB_CORE
>>>     symbol FB_CORE is selected by DRM_GEM_DMA_HELPER
>>>     symbol DRM_GEM_DMA_HELPER is selected by DRM_PANEL_ILITEK_ILI9341
>>>     symbol DRM_PANEL_ILITEK_ILI9341 depends on BACKLIGHT_CLASS_DEVICE
>>>
>>> BACKLIGHT_CLASS_DEVICE is user-selectable, so making drivers adapt to
>>> it is the correct approach in any case. For most drivers, backlight
>>> support is also configurable separately.
>>>
>>> v2:
>>> - s/BACKLIGHT_DEVICE_CLASS/BACKLIGHT_CLASS_DEVICE (Helge)
>>> - Fix fbdev driver-dependency corner case (Arnd)
>>>
>>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>>> ---
>>>   drivers/auxdisplay/Kconfig       |  2 +-
>>>   drivers/macintosh/Kconfig        |  1 +
>>>   drivers/staging/fbtft/Kconfig    |  1 +
>>>   drivers/video/fbdev/Kconfig      | 18 +++++++++++++-----
>>>   drivers/video/fbdev/core/Kconfig |  3 +--
>>>   5 files changed, 17 insertions(+), 8 deletions(-)
>>
>> Build fails which pmac32_defconfig :
>>
>>   LD      .tmp_vmlinux1
>> powerpc64-linux-ld: drivers/macintosh/via-pmu-backlight.o: in function 
>> `pmu_backlight_init':
>> via-pmu-backlight.c:(.init.text+0xc0): undefined reference to 
>> `backlight_device_register'
>> make[2]: *** [scripts/Makefile.vmlinux:77: vmlinux] Error 1
>> make[1]: *** [/home/chleroy/linux-powerpc/Makefile:1225: vmlinux] Error 2
> 
> The attached patch selects backlight support in the defconfigs that also 
> have PMAC_BACKLIGHT=y. Can you please apply it on top of the patchset 
> and report on the results?
> 

That works for the defconfig but it is still possible to change 
CONFIG_BACKLIGHT_CLASS_DEVICE manually.

If it is necessary for PMAC_BACKLIGHT then it shouldn't be possible to 
deselect it.