Re: [PATCH 2/8] drm/i915: Make the intel_device_info structure kept in dev_priv writable

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Feb 10, 2014 at 10:09:11AM +0100, Daniel Vetter wrote:
> On Fri, Feb 07, 2014 at 07:12:48PM +0000, Damien Lespiau wrote:
> > Turns out it'd be nice to change some device information at run-time or simply
> > have some code to fill in the info struct instead of having to declare the
> > values in 30+ structures.
> > 
> > What prompted this change is handling fused out display/pipe and tweaking
> > num_pipes at run-time, but I'm quite sure we'll find other flags/limits to
> > stick into dev_priv->info.
> > 
> > Most of the changes were done with a sed:
> > sed -i -e 's/dev_priv->info->/dev_priv->info./g' drivers/gpu/drm/i915/*[ch]
> > 
> > with a few tweaks to make it all work:
> > - Change the field definition in struct drm_i915_private
> > - adjust i915_dump_device_info()
> > - adjust i915_driver_load()
> > - adjust the INTEL_INFO() macro
> > 
> > v2: cast the info pointer returned by INTEL_INFO() to be const to catch
> >     uses that would modify the structure post-initialization.
> >     (Ville Syrjälä)
> > 
> > v3: Redo the patch onto latest drm-nightly,
> >     Keep the info field const to catch post initialization writes
> >     instead of the v2 solution,
> >     Use a direct structure copy for the initial info initialization to
> >     use the compiler type safety (Ville Syrjälä)
> > 
> > Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com> (for v2)
> > Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (for v2)
> > Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
> 
> [snip]
> 
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 728b9c3..f66699f 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -1390,7 +1390,7 @@ typedef struct drm_i915_private {
> >  	struct drm_device *dev;
> >  	struct kmem_cache *slab;
> >  
> > -	const struct intel_device_info *info;
> > +	const struct intel_device_info info;
> 
> Since every access should now go through the macro I think it'd be good to
> give this a __ prefix to make it clear that users better think twice
> before using it. Maybe as a patch on top of all this?

No. Everyone having to use the macro was a requirement of the v2 patch.
With v3 that requirement was lifted since the const is right there on
the struct itself. I think that was the whole point of v3.

-- 
Ville Syrjälä
Intel OTC