[Intel-gfx] [PATCH] drm/Kconfig: favor n for DRM_I915_PRELIMINARY_HW_SUPPORT

[Ben Widawsky]

On Tue, Aug 20, 2013 at 01:08:22AM +0100, Damien Lespiau wrote:
> On Mon, Aug 19, 2013 at 04:20:40PM -0700, Ben Widawsky wrote:
> > We generally don't want people or distros to use this option unless they
> > know what they're doing. I missed the initial conversation but it's
> > likely a way for people who have a built-in i915.ko and have no other
> > way to change the behavior.
>  
> It's to be able to have a config file to generate kernels supporting
> preliminary hardware, without having to always add the command line
> parameter or carry a patch or changing the bootloader configuration.
> 

Changing default module parameter options is not something we should be
solving with a CONFIG option. It is solvable with modeprobe.conf. The
unsolvable problem is for building in, which is the reason I agree this
patch is necessary at all. (The other being systems which don't have, or
have an ancient version of modprobe, but I don't believe that is the
target audience). Given the recent kernels allow us to break module
parameter "ABI" would be another (albeit less defensible) reason not to
use a CONFIG option. All this is, "whatever" though, since the patch is
already merged.

> > As such:
> > 	Set default to n
> > 	Display message for what users should select (N)
> > 	and while there, a small whitespace fix.
> > 
> > Cc Josh Triplett <josh at joshtriplett.org>
> 
> Missing the ':' so you didn't end up Ccing Josh.

Thanks a lot for catching that. CC'd now.

> 
> > Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> > ---
> >  drivers/gpu/drm/Kconfig | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> > index 62a06c7..ad4e369 100644
> > --- a/drivers/gpu/drm/Kconfig
> > +++ b/drivers/gpu/drm/Kconfig
> > @@ -171,12 +171,15 @@ config DRM_I915_KMS
> >  config DRM_I915_PRELIMINARY_HW_SUPPORT
> >  	bool "Enable preliminary support for prerelease Intel hardware by default"
> >  	depends on DRM_I915
> > +	default n
> 
> That's the default, you don't have to make it explicit (but of course it
> doesn't hurt). make oldconfig with this new option gives:
> 
>   Enable preliminary support for prerelease Intel hardware by default
>   (DRM_I915_PRELIMINARY_HW_SUPPORT) [N/y/?] (NEW)
> 

Right. We can drop it, I don't really care.

> >  	help
> >  	  Choose this option if you have prerelease Intel hardware and want the
> > -	  i915 driver to support it by default.  You can enable such support at
> > +	  i915 driver to support it by default. You can enable such support at
> 
> The Kconfig files have both styles, 2 spaces or 1 space after the '.'.

I learned something new here. We can drop this too then.

> 
> >  	  runtime with the module option i915.preliminary_hw_support=1; this
> >  	  option changes the default for that module option.
> >  
> > +	  If in doubt, say "N".
> > +

Heh. You didn't comment on the one part I really wanted to add ;-). The
rest of the patch doesn't matter much to me.

> >  config DRM_MGA
> >  	tristate "Matrox g200/g400"
> >  	depends on DRM && PCI
-- 
Ben Widawsky, Intel Open Source Technology Center