[PATCH] modesetting: allow switching from software to hardware cursors.

[Jasper St. Pierre]

Can you give an example of when drmSetCursor2 would fail sometimes but
not always, enough to switch back and forth actively?

I'm not a huge fan of the patch because now errors could cause really
bizarre double-cursor, or no-cursor flickering, since there is no
guarantee that the swapover happens in the same frame.

We sort-of tried this in Weston for something else (we rendered
certain windows in overlays) and had to turn it off and go to always
SW because of the obnoxious flickering, at least until atomic landed.

On Sat, Mar 12, 2016 at 3:54 AM, Michael Thayer
<michael.thayer at oracle.com> wrote:
> Hello,
>
> I would just like to politely draw attention to this again.  I would assume
> from the silence that the people who might review it don't think it is a
> completely wrong thing (that would not take long to say) but don't have the
> spare cycles to take a closer look.  Any idea when someone might have twenty
> minutes to review it?
>
> Regards,
>
> Michael
>
>
> On 06.03.2016 12:56, Michael Thayer wrote:
>>
>> Currently if modesetting ever fails to set a hardware cursor it will
>> switch
>> to using a software cursor and never go back.  Change this to try a
>> hardware
>> cursor first every time a new one is set.  This is needed because hardware
>> may be able to handle some cursors in harware and others not, or virtual
>> hardware may be able to handle hardware cursors at some times and not
>> others.
>>
>> Signed-off-by: Michael Thayer <michael.thayer at oracle.com>
>> ---
>> Made the commit message more verbose on Emil's request.
>>
>>   hw/xfree86/drivers/modesetting/drmmode_display.c | 47
>> ++++++++++--------------
>>   1 file changed, 20 insertions(+), 27 deletions(-)
>>
>> diff --git a/hw/xfree86/drivers/modesetting/drmmode_display.c
>> b/hw/xfree86/drivers/modesetting/drmmode_display.c
>> index 0d34ca1..36c3093 100644
>> --- a/hw/xfree86/drivers/modesetting/drmmode_display.c
>> +++ b/hw/xfree86/drivers/modesetting/drmmode_display.c
>> @@ -485,44 +485,36 @@ drmmode_set_cursor_position(xf86CrtcPtr crtc, int x,
>> int y)
>>       drmModeMoveCursor(drmmode->fd, drmmode_crtc->mode_crtc->crtc_id, x,
>> y);
>>   }
>>
>> -static void
>> +static Bool
>>   drmmode_set_cursor(xf86CrtcPtr crtc)
>>   {
>>       drmmode_crtc_private_ptr drmmode_crtc = crtc->driver_private;
>>       drmmode_ptr drmmode = drmmode_crtc->drmmode;
>>       uint32_t handle = drmmode_crtc->cursor_bo->handle;
>>       modesettingPtr ms = modesettingPTR(crtc->scrn);
>> -    static Bool use_set_cursor2 = TRUE;
>>       int ret;
>>
>> -    if (use_set_cursor2) {
>> -        xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(crtc->scrn);
>> -        CursorPtr cursor = xf86_config->cursor;
>> -
>> -        ret =
>> -            drmModeSetCursor2(drmmode->fd,
>> drmmode_crtc->mode_crtc->crtc_id,
>> -                              handle, ms->cursor_width,
>> ms->cursor_height,
>> -                              cursor->bits->xhot, cursor->bits->yhot);
>> -        if (!ret)
>> -            return;
>> -        if (ret == -EINVAL)
>> -            use_set_cursor2 = FALSE;
>> -    }
>> +    xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(crtc->scrn);
>> +    CursorPtr cursor = xf86_config->cursor;
>>
>> -    ret = drmModeSetCursor(drmmode->fd, drmmode_crtc->mode_crtc->crtc_id,
>> handle,
>> -                           ms->cursor_width, ms->cursor_height);
>> +    ret =
>> +        drmModeSetCursor2(drmmode->fd, drmmode_crtc->mode_crtc->crtc_id,
>> +                          handle, ms->cursor_width, ms->cursor_height,
>> +                          cursor->bits->xhot, cursor->bits->yhot);
>> +    if (!ret)
>> +        return TRUE;
>>
>> -    if (ret) {
>> -        xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(crtc->scrn);
>> -        xf86CursorInfoPtr cursor_info = xf86_config->cursor_info;
>> +    /* -EINVAL can mean bad cursor parameters or Cursor2 API not
>> supported. */
>> +    if (ret == -EINVAL)
>> +        ret = drmModeSetCursor(drmmode->fd,
>> drmmode_crtc->mode_crtc->crtc_id,
>> +                               handle, ms->cursor_width,
>> ms->cursor_height);
>>
>> -        cursor_info->MaxWidth = cursor_info->MaxHeight = 0;
>> -        drmmode_crtc->drmmode->sw_cursor = TRUE;
>> -        /* fallback to swcursor */
>> -    }
>> +    if (ret)
>> +        return FALSE; /* fallback to swcursor */
>> +    return TRUE;
>>   }
>>
>> -static void
>> +static Bool
>>   drmmode_load_cursor_argb(xf86CrtcPtr crtc, CARD32 *image)
>>   {
>>       modesettingPtr ms = modesettingPTR(crtc->scrn);
>> @@ -537,7 +529,8 @@ drmmode_load_cursor_argb(xf86CrtcPtr crtc, CARD32
>> *image)
>>           ptr[i] = image[i];      // cpu_to_le32(image[i]);
>>
>>       if (drmmode_crtc->cursor_up)
>> -        drmmode_set_cursor(crtc);
>> +        return drmmode_set_cursor(crtc);
>> +    return TRUE;
>>   }
>>
>>   static void
>> @@ -799,7 +792,7 @@ static const xf86CrtcFuncsRec drmmode_crtc_funcs = {
>>       .set_cursor_position = drmmode_set_cursor_position,
>>       .show_cursor = drmmode_show_cursor,
>>       .hide_cursor = drmmode_hide_cursor,
>> -    .load_cursor_argb = drmmode_load_cursor_argb,
>> +    .load_cursor_argb_check = drmmode_load_cursor_argb,
>>
>>       .gamma_set = drmmode_crtc_gamma_set,
>>       .destroy = NULL,            /* XXX */
>>
>
> --
> Michael Thayer | VirtualBox engineer
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-- 
  Jasper