Re: [PATCH 1/2] drm/fb-helper: Don't clobber the display palette when fbdev isn't bound

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, May 27, 2013 at 06:44:56PM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Perform the drm_fb_helper_is_bound() check to avoid clobbering the
> display palette of some other KMS client.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

You might want to mention that you're also fixing up the locking a bit ;-)
The lack of that would be much more obvious if the fbdev helper would use
the real kms gamma interface instead of it's own driver backdoor. But
that's a different patch to write.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/drm_fb_helper.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index b78cbe7..1b6ca23 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -626,12 +626,19 @@ static int setcolreg(struct drm_crtc *crtc, u16 red, u16 green,
>  int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
>  {
>  	struct drm_fb_helper *fb_helper = info->par;
> +	struct drm_device *dev = fb_helper->dev;
>  	struct drm_crtc_helper_funcs *crtc_funcs;
>  	u16 *red, *green, *blue, *transp;
>  	struct drm_crtc *crtc;
>  	int i, j, rc = 0;
>  	int start;
>  
> +	drm_modeset_lock_all(dev);
> +	if (!drm_fb_helper_is_bound(fb_helper)) {
> +		drm_modeset_unlock_all(dev);
> +		return -EBUSY;
> +	}
> +
>  	for (i = 0; i < fb_helper->crtc_count; i++) {
>  		crtc = fb_helper->crtc_info[i].mode_set.crtc;
>  		crtc_funcs = crtc->helper_private;
> @@ -654,10 +661,12 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
>  
>  			rc = setcolreg(crtc, hred, hgreen, hblue, start++, info);
>  			if (rc)
> -				return rc;
> +				goto out;
>  		}
>  		crtc_funcs->load_lut(crtc);
>  	}
> + out:
> +	drm_modeset_unlock_all(dev);
>  	return rc;
>  }
>  EXPORT_SYMBOL(drm_fb_helper_setcmap);
> -- 
> 1.8.1.5
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch