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modesetting: Improve the ms_flush_drm_events() API.

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Previously, ms_flush_drm_events() returned a boolean value, and it was
very easy to interpret the meaning incorrectly.  Now, we return an
integer value.

The possible outcomes of this call are:
- poll() raised an error (formerly TRUE, now -1 - poll's return value)
- poll() said there are no events (formerly TRUE, now 0).
- drmHandleEvent() raised an error (formerly FALSE, now the negative
  value returned by drmHandleEvent).
- An event was successfully handled (formerly TRUE, now 1).

The nice part is that this allows you to distinguish errors (< 0),
nothing to do (= 0), and success (1).  We no longer conflate errors
with success.

v2: Change ms_present_queue_vblank to < 0 instead of <= 0, fixing an
    unintentional behavior change.  libdrm may return EBUSY if it's
    received EINTR for more than a second straight; just keep retrying
    in that case.  Suggested by Jasper St. Pierre.

Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Kenneth Graunke 2015-02-08 17:21:58 -08:00 committed by Dave Airlie
parent 7328fb3f2b
commit f6853baeba
1 changed files with 19 additions and 4 deletions
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23
hw/xfree86/drivers/modesetting/present.c
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@ -72,8 +72,11 @@ ms_present_get_ust_msc(RRCrtcPtr crtc, CARD64 *ust, CARD64 *msc)
/*
* Flush the DRM event queue when full; makes space for new events.
*
* Returns a negative value on error, 0 if there was nothing to process,
* or 1 if we handled any events.
*/
static Bool
static int
ms_flush_drm_events(ScreenPtr screen)
{
ScrnInfoPtr scrn = xf86ScreenToScrn(screen);
@ -86,10 +89,19 @@ ms_flush_drm_events(ScreenPtr screen)
r = poll(&p, 1, 0);
} while (r == -1 && (errno == EINTR || errno == EAGAIN));
/* If there was an error, r will be < 0. Return that. If there was
* nothing to process, r == 0. Return that.
*/
if (r <= 0)
return TRUE;
return r;
return drmHandleEvent(ms->fd, &ms->event_context) >= 0;
/* Try to handle the event. If there was an error, return it. */
r = drmHandleEvent(ms->fd, &ms->event_context);
if (r < 0)
return r;
/* Otherwise return 1 to indicate that we handled an event. */
return 1;
}
/*
@ -159,7 +171,10 @@ ms_present_queue_vblank(RRCrtcPtr crtc,
ret = drmWaitVBlank(ms->fd, &vbl);
if (!ret)
break;
if (errno != EBUSY || !ms_flush_drm_events(screen))
/* If we hit EBUSY, then try to flush events. If we can't, then
* this is an error.
*/
if (errno != EBUSY || ms_flush_drm_events(screen) < 0)
return BadAlloc;
}
DebugPresent(("\t\tmq %lld seq %u msc %llu (hw msc %u)\n",