linux-kernel - Re: [PATCH v2] drm: support hotspot for universal plane cursors

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Date:	Tue, 17 Nov 2015 17:29:35 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	John Keeping <john@...anate.com>
Cc:	Ville Syrjälä 
	<ville.syrjala@...ux.intel.com>, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	Michel Dänzer <michel.daenzer@....com>,
	Alex Deucher <alexdeucher@...il.com>
Subject: Re: [PATCH v2] drm: support hotspot for universal plane cursors

On Tue, Nov 17, 2015 at 03:59:43PM +0000, John Keeping wrote:
> On Tue, 17 Nov 2015 17:39:32 +0200, Ville Syrjälä wrote:
> 
> > On Tue, Nov 17, 2015 at 03:05:34PM +0000, John Keeping wrote:
> > > The request's hot_x and hot_y are set correctly for both
> > > DRM_IOCTL_MODE_CURSOR and DRM_IOCTL_MODE_CURSOR2 so we just need to
> > > save the values and then apply the offset to the cursor plane when
> > > the cursor moves.
> > > 
> > > Signed-off-by: John Keeping <john@...anate.com>
> > > ---
> > > v2:
> > >   - add kerneldoc for hot_x and hot_y in struct drm_crtc
> > > 
> > >  drivers/gpu/drm/drm_crtc.c | 11 +++++++----
> > >  include/drm/drm_crtc.h     |  6 ++++++
> > >  2 files changed, 13 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> > > index 720a153..40f5b84 100644
> > > --- a/drivers/gpu/drm/drm_crtc.c
> > > +++ b/drivers/gpu/drm/drm_crtc.c
> > > @@ -2831,6 +2831,9 @@ static int drm_mode_cursor_universal(struct
> > > drm_crtc *crtc, DRM_DEBUG_KMS("failed to wrap cursor buffer in drm
> > > framebuffer\n"); return PTR_ERR(fb);
> > >  			}
> > > +
> > > +			crtc->hot_x = req->hot_x;
> > > +			crtc->hot_y = req->hot_y;
> > >  		} else {
> > >  			fb = NULL;
> > >  		}
> > > @@ -2841,11 +2844,11 @@ static int drm_mode_cursor_universal(struct
> > > drm_crtc *crtc, }
> > >  
> > >  	if (req->flags & DRM_MODE_CURSOR_MOVE) {
> > > -		crtc_x = req->x;
> > > -		crtc_y = req->y;
> > > +		crtc_x = req->x - crtc->hot_x;
> > > +		crtc_y = req->y - crtc->hot_y;
> > >  	} else {
> > > -		crtc_x = crtc->cursor_x;
> > > -		crtc_y = crtc->cursor_y;
> > > +		crtc_x = crtc->cursor_x - crtc->hot_x;
> > > +		crtc_y = crtc->cursor_y - crtc->hot_y;  
> > 
> > Why does the location of the hotspot affect the plane position?
> 
> hot_{x,y} specify the location of the active pixel within the cursor
> plane and cursor_{x,y} specify the location of the active pixel on the
> display so we need to offset the plane position in order for the active
> pixel to be in the correct place.

Nope, hot_x/y is just for virtual machines to indicate where the logical
cursor position is within the cursor plane. It should have 2 effect on how
something is displayed. And no, I have absolutely no idea why radeon is
pulling some tricks here, which have been added in

commit 78b1a6010b46a69bcd47b723a80f92693f26d17b
Author: Michel Dänzer <michel.daenzer@....com>
Date:   Tue Nov 18 18:00:08 2014 +0900

    drm/radeon: Use cursor_set2 hook for enabling / disabling the HW cursor

Michel/Alex, can you please shed some light onto this? radeon is the only
driver doing this, making this interface inconsistent. Is the ddx doing
something funny compared to -modeseting or weston?

At least a quick look in the -ati sources didn't even show a user for
this, it's still using the old cursor ioctl. And there's no other
indication in the commit of a bug or anything. Can we perhaps just revert
this?

Cheers, Daniel

> 
> > >  	}
> > >  
> > >  	if (fb) {
> > > diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> > > index 3f0c690..2be4414 100644
> > > --- a/include/drm/drm_crtc.h
> > > +++ b/include/drm/drm_crtc.h
> > > @@ -404,6 +404,8 @@ struct drm_crtc_funcs {
> > >   * @cursor: cursor plane for this CRTC
> > >   * @cursor_x: current x position of the cursor, used for universal
> > > cursor planes
> > >   * @cursor_y: current y position of the cursor, used for universal
> > > cursor planes
> > > + * @hot_x: x-coordinate of cursor hotspot, used for universal
> > > cursor planes
> > > + * @hot_y: y-coordinate of cursor hotspot, used for universal
> > > cursor planes
> > >   * @enabled: is this CRTC enabled?
> > >   * @mode: current mode timings
> > >   * @hwmode: mode timings as programmed to hw regs
> > > @@ -445,6 +447,10 @@ struct drm_crtc {
> > >  	int cursor_x;
> > >  	int cursor_y;
> > >  
> > > +	/* hotspot of cursor */
> > > +	int hot_x;
> > > +	int hot_y;
> > > +
> > >  	bool enabled;
> > >  
> > >  	/* Requested mode from modesetting. */
> > > -- 
> > > 2.6.3.462.gbe2c914
> > > 
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel@...ts.freedesktop.org
> > > http://lists.freedesktop.org/mailman/listinfo/dri-devel  
> > 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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