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

[Helge Deller]

On 12/10/24 16:41, Thomas Zimmermann wrote:
> Hi
>
>
> Am 10.12.24 um 15:34 schrieb Helge Deller:
>> On 12/10/24 15:29, Helge Deller wrote:
>>> On 12/10/24 15:09, Thomas Zimmermann wrote:
>>>> diff --git a/drivers/staging/fbtft/Kconfig b/drivers/staging/fbtft/Kconfig
>>>> index 77ab44362f16..577e91ff7bf6 100644
>>>> --- a/drivers/staging/fbtft/Kconfig
>>>> +++ b/drivers/staging/fbtft/Kconfig
>>>> @@ -3,6 +3,7 @@ menuconfig FB_TFT
>>>>       tristate "Support for small TFT LCD display modules"
>>>>       depends on FB && SPI
>>>>       depends on FB_DEVICE
>>>> +    depends on BACKLIGHT_DEVICE_CLASS
>>>
>>> Typo. Should be BACKLIGHT_CLASS_DEVICE...
>
> Ah, thanks. I'll better check the rest of the series for similar mistakes.
>
>>
>> Beside the typo:
>> In this case, doesn't it make sense to "select BACKLIGHT_DEVICE_CLASS" instead?
>
> That causes the dependency error mentioned in the commit message. This time it's just for fbtft instead of shmobilefb.
>
>> If people want the fbtft, backlight support should be enabled too.
>
> As a user-visible option, it should not be auto-selected
> unnecessarily.

Right, it should not be auto-selected.
Unless if fbtft really needs it enabled to function.
IMHO all fb/drm drivers have higher priority than some low-level
background backlight controller code.

> The DRM panel drivers already depend on the backlight
> instead of selecting it. It's the correct approach.

Sounds wrong IMHO.

> As I mentioned
> in the cover letter, the few remaining driver that select it should
> probably be updated.

That dependency sounds weird, but maybe I simply misunderstand your logic...?

As a Linux end user I usually know which graphic cards are in my machine
and which ones I want to enable.
But as a normal user I think I shouldn't be expected to know
that I first need to enable the "backlight class device"
so that I'm then able to afterwards enable the fbtft (or any other drm/fb driver).

Am I wrong?

Helge