Re: [PATCH 1/2] drm: provide a helper for the encoder possible_crtcs mask

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Mon, Jan 13, 2014 at 02:50:46PM +0100, David Herrmann wrote:
> Hi Russel
> 
> On Mon, Jan 13, 2014 at 1:47 PM, Russell King - ARM Linux
> <linux@arm.linux.org.uk> wrote:
> > On Mon, Jan 13, 2014 at 12:58:54PM +0100, David Herrmann wrote:
> >> Does that -1 ever make sense? We don't support mode-object-hotplugging
> >> so all "drm_crtc" objects are known at initialization time. I'd rather
> >> put a BUG() here than a silent -1. This also makes drm_crtc_mask()
> >> redundant.
> >
> > I disagree with that last statement.  drm_crtc_mask() is still useful
> > for converting to the mask, rather than having that open coded all
> > over the place.  It probably makes more sense for drm_crtc_mask() to
> > become a helper in a header file though.
> 
> Thierry renamed your helper to drm_crtc_index() and added
> drm_crtc_mask(). If we remove the -1, drm_crtc_mask() is redundant as
> it just calls drm_crtc_index(). So I cannot follow what you mean by
> "open coded all over the place". I guess you were talking about
> drm_crtc_index()?

+uint32_t drm_crtc_mask(struct drm_crtc *crtc)
+{
+       int i = drm_crtc_index(crtc);
+
+       return i < 0 ? 0 : 1 << i;
+}
+EXPORT_SYMBOL(drm_crtc_mask);

When drm_crtc_index() no longer returns negative numbers, this becomes:

+uint32_t drm_crtc_mask(struct drm_crtc *crtc)
+{
+       return 1 << drm_crtc_index(crtc);
+}
+EXPORT_SYMBOL(drm_crtc_mask);

Notice the conversion from an index returned by drm_crtc_index() to a
bitmask.

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