Re: [PATCH 1/2] drm/i915: Don't clobber the addfb2 ioctl params

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

On Wed, Nov 11, 2015 at 05:20:10PM +0000, Chris Wilson wrote:
> On Wed, Nov 11, 2015 at 07:11:28PM +0200, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > We try to convert the old way of of specifying fb tiling (obj->tiling)
> > into the new fb modifiers. We store the result in the passed in mode_cmd
> > structure. But that structure comes directly from the addfb2 ioctl, and
> > gets copied back out to userspace, which means we're clobbering the
> > modifiers that the user provided (all 0 since the DRM_MODE_FB_MODIFIERS
> > flag wasn't even set by the user). Hence if the user reuses the struct
> > for another addfb2, the ioctl will be rejected since it's now asking for
> > some modifiers w/o the flag set.
> 
> What do we actually pass back to userspace through the struct?

The fb id.

> Do we
> just want to
> -#define DRM_IOCTL_MODE_ADDFB2          DRM_IOWR(0xB8, struct drm_mode_fb_cmd2)
> +#define DRM_IOCTL_MODE_ADDFB2          DRM_IOR(0xB8, struct drm_mode_fb_cmd2
> instead?
> -Chris
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre

-- 
Ville Syrjälä
Intel OTC