Den 03.10.2017 16.58, skrev Noralf Trønnes:
Den 02.10.2017 10.13, skrev Jani Nikula:
On Mon, 02 Oct 2017, Daniel Vetter <daniel@xxxxxxxx> wrote:
Also adding Jani, who looked at the backlight Kconfig mess in the past.
I've even sent patches to fix some of the dependency mess, but the
problem is social not technical. The problem is that people think
"select" is more convenient than "depends" because they can just enable
a config that way, while "depends" would require finding and enabling
all the dependencies before the menu option even shows up.
I don't deny, that's annoying. But it's also abuse of select, see
Documentation/kbuild/kconfig-language.txt:
Note:
select should be used with care. select will force
a symbol to a value without visiting the dependencies.
By abusing select you are able to select a symbol FOO even
if FOO depends on BAR that is not set.
In general use select only for non-visible symbols
(no prompts anywhere) and for symbols with no dependencies.
That will limit the usefulness but on the other hand avoid
the illegal configurations all over.
The real fix would be making finding and enabling dependencies
recursively more convenient, but I don't see that happening anytime
soon.
If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
and CONFIG_BACKLIGHT_CLASS_DEVICE=m.
So we can either do:
menuconfig DRM
depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
No, this was the thing that didn't work:
drivers/gpu/drm/Kconfig:7: symbol DRM depends on BACKLIGHT_CLASS_DEVICE
drivers/video/backlight/Kconfig:158: symbol BACKLIGHT_CLASS_DEVICE is
selected by DRM_RADEON
drivers/gpu/drm/Kconfig:164: symbol DRM_RADEON depends on DRM
Or we can:
-#ifdef CONFIG_OF
+#if IS_ENABLED(CONFIG_OF) && IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
struct backlight_device *of_find_backlight_by_node(struct device_node
*node);
#else
static inline struct backlight_device *
Using the second one it won't be obvious to users why backlight
doesn't work,
they have after all enabled backlight (but as module and DRM builtin).
So I suppose the first one is preferred.
What effect will such a change have on an existing configuration where
DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
be disabled?
Noralf.
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