Re: Dependencies in the HID subsystem

[Jean Delvare <jdelvare@suse.de>]

Hi David,

Sorry for the late reply.

Le Thursday 30 May 2013 à 00:23 +0200, David Herrmann a écrit :
> Hi
> 
> On Wed, May 29, 2013 at 10:52 PM, Jiri Kosina <jkosina@suse.cz> wrote:
> > On Wed, 29 May 2013, Jean Delvare wrote:
> >
> >> I am worried and confused by some Kconfig dependencies in the HID
> >> subsystem.
> >>
> >> There are 11 HID device drivers which are defined in drivers/hid/Kconfig
> >> with:
> >>
> >>       tristate "..." if EXPERT
> >>       default !EXPERT
> >>
> >> Unless EXPERT is enabled (and that's not the default), these driver
> >> entries are hidden and automatically selected. If CONFIG_HID=m, they are
> >> selected as modules. If CONFIG_HID=y, they are built into the kernel. So
> >> it is impossible to have CONFIG_HID=y and build these device drivers as
> >> modules - as device drivers typically are.
> >>
> >> I would like to understand the reasoning behind this complexity. What is
> >> so special about these 11 drivers, that we can't just let the (kernel
> >> configuring) user chose if he/she wants them and in what form?
> 
> For several reason I recommend CONFIG_EXPERT for all users, anyway.
> But apart from that, what's wrong with "default y" and dropping any
> CONFIG_EXPERT dependency? We can still keep the "tristate '..' if
> EXPERT".

There is a contradiction in your proposal. The tristate "..." if EXPERT
_is_ a CONFIG_EXPERT dependency, and that's exactly what I would like to
see go away. "default y" would be fine with me.

> The CONFIG_EXPERT descriptions says "this option allows certain base
> kernel options and settings to be disabled or tweaked". This really
> doesn't say anything about "disable any non-standard options if this
> is selected". So why do we default to "n" if CONFIG_EXPERT is
> selected? This always bothered me because I don't expect the config to
> change if I select it.

I agree that this kind of option-dependent default value can easily be
confusing. I suppose it was done that way for historical reasons, to
minimize the effect of changes while the HID subsystem was being
reworked. But I would like to see it go away now.

-- 
Jean Delvare
Suse L3

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