sna: Wrap rrGetInfo so that we can probe when udev is not active

If the ddx is configured without udev support, we do not receive
notifications when the MST topology is changed. This leads us to query
the kernel for bad connectors, and so we end up reporting an unknown
connection status for them, which the user and client often find
confusing. However, we can not simply act upon the detection failure as
we are too deep inside the callback chain and cannot change the arrays of
known connectors whilst iterating over them. A neat compromise is to
hook into the rrGetInfo call chain and poll for MST changes before we
report back the current configuration.

References: https://bugs.freedesktop.org/show_bug.cgi?id=84718
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 50 insertions, 6 deletions

diff --git a/src/sna/sna_driver.c b/src/sna/sna_driver.c
index f28ca872..a09aa986 100644
--- a/src/sna/sna_driver.c
+++ b/src/sna/sna_driver.c
@@ -59,6 +59,7 @@ USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 #include <sys/ioctl.h>
 #include <sys/fcntl.h>
+#include <sys/poll.h>
 #include "i915_drm.h"
 
 #ifdef HAVE_VALGRIND
@@ -866,6 +867,22 @@ err_dev:
 	goto out;
 }
 
+static bool sna_uevent_poll(struct sna *sna)
+{
+	struct pollfd pfd;
+
+	if (sna->uevent_monitor == NULL)
+		return false;
+
+	pfd.fd = udev_monitor_get_fd(sna->uevent_monitor);
+	pfd.events = POLLIN;
+
+	if (poll(&pfd, 1, 0) > 0)
+		sna_handle_uevents(pfd.fd, sna);
+
+	return true;
+}
+
 static void
 sna_uevent_fini(struct sna *sna)
 {
@@ -887,9 +904,21 @@ sna_uevent_fini(struct sna *sna)
 }
 #else
 static void sna_uevent_init(struct sna *sna) { }
+static bool sna_uevent_poll(struct sna *sna) { return false; }
 static void sna_uevent_fini(struct sna *sna) { }
 #endif /* HAVE_UDEV */
 
+static Bool
+sna_randr_getinfo(ScreenPtr screen, Rotation *rotations)
+{
+	struct sna *sna = to_sna_from_screen(screen);
+
+	if (!sna_uevent_poll(sna))
+		sna_mode_discover(sna);
+
+	return sna->mode.rrGetInfo(screen, rotations);
+}
+
 static void sna_leave_vt(VT_FUNC_ARGS_DECL)
 {
 	SCRN_INFO_PTR(arg);
@@ -1035,6 +1064,25 @@ agp_aperture_size(struct pci_device *dev, int gen)
 }
 
 static Bool
+sna_mode_init(struct sna *sna, ScreenPtr screen)
+{
+	rrScrPrivPtr rp;
+
+	if (!xf86CrtcScreenInit(screen))
+		return FALSE;
+
+	xf86RandR12SetRotations(screen, RR_Rotate_All | RR_Reflect_All);
+	xf86RandR12SetTransformSupport(screen, TRUE);
+
+	/* Wrap RR queries to catch pending MST topology changes */
+	rp = rrGetScrPriv(screen);
+	sna->mode.rrGetInfo = rp->rrGetInfo;
+	rp->rrGetInfo = sna_randr_getinfo;
+
+	return TRUE;
+}
+
+static Bool
 sna_screen_init(SCREEN_INIT_ARGS_DECL)
 {
 	ScrnInfoPtr scrn = xf86ScreenToScrn(screen);
@@ -1134,12 +1182,9 @@ sna_screen_init(SCREEN_INIT_ARGS_DECL)
 	sna->CloseScreen = screen->CloseScreen;
 	screen->CloseScreen = sna_early_close_screen;
 
-	if (!xf86CrtcScreenInit(screen))
+	if (!sna_mode_init(sna, screen))
 		return FALSE;
 
-	xf86RandR12SetRotations(screen, RR_Rotate_All | RR_Reflect_All);
-	xf86RandR12SetTransformSupport(screen, TRUE);
-
 	if (!miCreateDefColormap(screen))
 		return FALSE;
 
@@ -1151,6 +1196,7 @@ sna_screen_init(SCREEN_INIT_ARGS_DECL)
 
 	xf86DPMSInit(screen, sna_dpms_set, 0);
 
+	sna_uevent_init(sna);
 	sna_video_init(sna, screen);
 	sna_dri_init(sna, screen);
 
@@ -1165,8 +1211,6 @@ sna_screen_init(SCREEN_INIT_ARGS_DECL)
 
 	sna->suspended = FALSE;
 
-	sna_uevent_init(sna);
-
 	return TRUE;
 }