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

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Feb 10, 2014 at 02:53:29PM +0200, Ville Syrjälä wrote:
> 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.

Oops, I've missed that v3 has the const even on the dev_priv->info pointer
now. No need for any gratious rename fests then imo.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch