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

[Thomas Zimmermann]

Hi


Am 13.12.24 um 09:33 schrieb 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.

If you disable CONFIG_BACKLIGHT_CLASS_DEVICE, shouldn't that 
auto-disable PMAC_BACKLIGHT as well?

Best regards
Thomas


-- 
--
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)