[PATCH xserver] modesetting: allow switching from software to hardware cursors (v3).

Thu Sep 15 14:40:19 UTC 2016

Hello Hans,

On 15.09.2016 16:12, Hans de Goede wrote:
> Hi,
>
> On 15-09-16 12:04, 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.
>>
>> Changes since v1 and v2:
>>  * take into account the switch to load_cursor_argb_check
>>  * altogether drop the fall-back path to SetCursor() if SetCursor2()
>> fails:
>>    SetCursor2() has been supported in released kernels for three years
>> now,
>>    and I think a software cursor fallback is acceptable if anyone has
>> to use
>>    1.19 with such an old kernel
>
> Nack for this change, the software cursor experience really is sub-optimal,
> I'm pretty sure people which are stuck on old kernels for some reason
> will greatly prefer needing 2 ioctls per set_cursor (it is not like that
> happens 1000-s times a second) vs software cursors.
>
> I mean isn't the whole purpose of this patch-set to avoid software
> cursors in virtualbox ?

My assumption was that people stuck with old kernels would also stick to 
older X servers, but as I said, your call there.

>>  * drop the special case for loading a cursor sprite when the cursor is
>>    hidden: we set HARDWARE_CURSOR_UPDATE_UNHIDDEN, so all calls to
>>    load_cursor will be followed by calls to show_cursor unless the load
>>    fails (when a call to hide_cursor should follow)
>
> Nack again, have you read the actual commit msg of the commit which
> introduced the change ?   :
>
> https://cgit.freedesktop.org/xorg/xserver/commit/hw/xfree86/drivers/modesetting?id=af916477c65a083ec496ac3f088d766b410e8b6e
>
>
> If we revert this change (which really should be in a separate patch
> btw) then software cursor fallback will not work reliably because
> the first drmmode_load_cursor_argb_check() will succeed as
> it is a nop when the cursor is hidden, at which point the server
> will continue trying to use the hw-cursor until the cursor
> is changed to a different cursor.

I did actually read the commit message, as well as the patch itself.  My 
patch removes the problem which that patch was intended to fix, as 
looking at the rest of the server and driver code it clearly makes no 
sense to skip the set_cursor call when the cursor is hidden.

> This makes me wonder if your change is a good idea at all, I'm
> getting the feeling that the whole dynamic now we support hw cursors
> now we don't trick virtualbox is playing is really just a bad
> idea...

Again, your call.  As far as I know though, there is also physical 
hardware which can display some cursors but not others and which would 
also need a change on these lines.

If you can live with the second part of the change which you commented 
on I can change the first.  Without the second change the patch does not 
work in its current form.

Regards,

Michael

> Regards,
>
> Hans
>
>
>
>
>
>>
>> Signed-off-by: Michael Thayer <michael.thayer at oracle.com>
>> ---
>> I hope that you are happy with the change I made to remove the
>> set_cursor1
>> fall-back (it does rather simplify the code!); if not I will send v4.
>>
>>  hw/xfree86/drivers/modesetting/drmmode_display.c | 40
>> ++++--------------------
>>  hw/xfree86/drivers/modesetting/drmmode_display.h |  2 --
>>  2 files changed, 6 insertions(+), 36 deletions(-)
>>
>> diff --git a/hw/xfree86/drivers/modesetting/drmmode_display.c
>> b/hw/xfree86/drivers/modesetting/drmmode_display.c
>> index 6b933e4..bf5ca32 100644
>> --- a/hw/xfree86/drivers/modesetting/drmmode_display.c
>> +++ b/hw/xfree86/drivers/modesetting/drmmode_display.c
>> @@ -756,33 +756,12 @@ drmmode_set_cursor(xf86CrtcPtr crtc)
>>      drmmode_ptr drmmode = drmmode_crtc->drmmode;
>>      uint32_t handle = drmmode_crtc->cursor_bo->handle;
>>      modesettingPtr ms = modesettingPTR(crtc->scrn);
>> -    int ret;
>> -
>> -    if (!drmmode_crtc->set_cursor2_failed) {
>> -        CursorPtr cursor = xf86CurrentCursor(crtc->scrn->pScreen);
>> -
>> -        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;
>> -
>> -        drmmode_crtc->set_cursor2_failed = TRUE;
>> -    }
>> -
>> -    ret = drmModeSetCursor(drmmode->fd,
>> drmmode_crtc->mode_crtc->crtc_id, handle,
>> -                           ms->cursor_width, ms->cursor_height);
>> +    CursorPtr cursor = xf86CurrentCursor(crtc->scrn->pScreen);
>>
>> -    if (ret) {
>> -        xf86CrtcConfigPtr xf86_config =
>> XF86_CRTC_CONFIG_PTR(crtc->scrn);
>> -        xf86CursorInfoPtr cursor_info = xf86_config->cursor_info;
>> -
>> -        cursor_info->MaxWidth = cursor_info->MaxHeight = 0;
>> -        drmmode_crtc->drmmode->sw_cursor = TRUE;
>> -        /* fallback to swcursor */
>> -        return FALSE;
>> -    }
>> +    if (drmModeSetCursor2(drmmode->fd, drmmode_crtc->mode_crtc->crtc_id,
>> +                          handle, ms->cursor_width, ms->cursor_height,
>> +                          cursor->bits->xhot, cursor->bits->yhot))
>> +        return FALSE; /* fallback to swcursor */
>>      return TRUE;
>>  }
>>
>> @@ -809,14 +788,7 @@ drmmode_load_cursor_argb_check(xf86CrtcPtr crtc,
>> CARD32 *image)
>>      for (i = 0; i < ms->cursor_width * ms->cursor_height; i++)
>>          ptr[i] = image[i];      // cpu_to_le32(image[i]);
>>
>> -    if (drmmode_crtc->cursor_up ||
>> !drmmode_crtc->first_cursor_load_done) {
>> -        Bool ret = drmmode_set_cursor(crtc);
>> -        if (!drmmode_crtc->cursor_up)
>> -            drmmode_hide_cursor(crtc);
>> -        drmmode_crtc->first_cursor_load_done = TRUE;
>> -        return ret;
>> -    }
>> -    return TRUE;
>> +    return drmmode_set_cursor(crtc);
>>  }
>>
>>  static void
>> diff --git a/hw/xfree86/drivers/modesetting/drmmode_display.h
>> b/hw/xfree86/drivers/modesetting/drmmode_display.h
>> index 50976b8..f774250 100644
>> --- a/hw/xfree86/drivers/modesetting/drmmode_display.h
>> +++ b/hw/xfree86/drivers/modesetting/drmmode_display.h
>> @@ -92,8 +92,6 @@ typedef struct {
>>      int dpms_mode;
>>      struct dumb_bo *cursor_bo;
>>      Bool cursor_up;
>> -    Bool set_cursor2_failed;
>> -    Bool first_cursor_load_done;
>>      uint16_t lut_r[256], lut_g[256], lut_b[256];
>>
>>      drmmode_bo rotate_bo;
>>

-- 
Michael Thayer | VirtualBox engineer
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