Date:	Tue, 17 Nov 2015 12:07:24 -0500
From:	Alex Deucher <alexdeucher@...il.com>
To:	John Keeping <john@...anate.com>,
	Ville Syrjälä <ville.syrjala@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Maling list - DRI developers 
	<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 11:29 AM, Daniel Vetter <daniel@...ll.ch> wrote:
> 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?

We use this is xf86-video-ati.  See:
http://cgit.freedesktop.org/xorg/driver/xf86-video-ati/commit/?id=c9f8f642fd495937400618a4fc25ecae3f8888fc
Our hw cursor has a hotspot register that needs to be programmed for
proper operation.  I don't remember the details of the specific bug.
Michel can provide more info.

Alex

>
> 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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