Re: [PATCH v2 1/3] fbdev: Fix recursive dependencies wrt BACKLIGHT_CLASS_DEVICE
From: "Arnd Bergmann" <arnd@arndb.de>
Date: 2024-12-12 21:04:52
Also in:
dri-devel, linux-staging, linuxppc-dev
On Thu, Dec 12, 2024, at 19:44, Helge Deller wrote:
quoted hunk ↗ jump to hunk
On 12/12/24 11:04, Thomas Zimmermann wrote:quoted
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 [...]I think in the fbdev drivers themselves you should do: select BACKLIGHT_CLASS_DEVICE instead of "depending" on it. This is the way as it's done in the DRM tiny and the i915/gma500 DRM drivers. So, something like:--- a/drivers/staging/fbtft/Kconfig tristate "Support for small TFT LCD display modules" depends on FB && SPI depends on FB_DEVICE + select BACKLIGHT_DEVICE_CLASS depends on GPIOLIB || COMPILE_TEST select FB_BACKLIGHTconfig FB_BACKLIGHT tristate depends on FB - select BACKLIGHT_CLASS_DEVICE + depends on BACKLIGHT_CLASS_DEVICE Would that fix the dependency warning?
The above is generally a mistake and the root cause of the
dependency loops. With very few exceptions, the solution in
these cases is to find the inconsistent 'select' and change
it into 'depends on'.
I actually have a few more patches like this that I've
been carrying for years now, e.g. one that changes all the
'select I2C' into appropriate dependencies.
Arnd