[RESEND PATCH i-g-t v3 2/5] igt_kms: Add helpers for watching for sysfs hotplug events

[Lyude <lyude@redhat.com>]

This adds some basic helpers for connecting to udev and watching for
sysfs hotplug events.

Cc: Tomeu Vizoso <tomeu@tomeuvizoso.net>
Signed-off-by: Lyude <lyude@redhat.com>

Changes since v1:
- Remove unused arg from documentation
Changes since v2:
- Make udev_monitor explicit so that we can use this for detecting FSMs
  from the Chamelium in rpc calls
---
 lib/igt_kms.c | 111 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_kms.h |   7 ++++
 2 files changed, 118 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index d104734..e36c0b8 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -38,6 +38,10 @@
 #elif HAVE_SYS_KD_H
 #include <sys/kd.h>
 #endif
+#ifdef HAVE_UDEV
+#include <libudev.h>
+#include <poll.h>
+#endif
 #include <errno.h>
 #include <time.h>
 
@@ -2921,6 +2925,113 @@ void igt_reset_connectors(void)
 			      "detect");
 }
 
+#ifdef HAVE_UDEV
+
+/**
+ * igt_watch_hotplug:
+ *
+ * Begin monitoring udev for sysfs hotplug events.
+ *
+ * Returns: a udev monitor for detecting hotplugs on
+ */
+struct udev_monitor *igt_watch_hotplug(void)
+{
+	struct udev *udev;
+	struct udev_monitor *mon;
+	int ret, flags, fd;
+
+	udev = udev_new();
+	igt_assert(udev != NULL);
+
+	mon = udev_monitor_new_from_netlink(udev, "udev");
+	igt_assert(mon != NULL);
+
+	ret = udev_monitor_filter_add_match_subsystem_devtype(mon,
+							      "drm",
+							      "drm_minor");
+	igt_assert_eq(ret, 0);
+	ret = udev_monitor_filter_update(mon);
+	igt_assert_eq(ret, 0);
+	ret = udev_monitor_enable_receiving(mon);
+	igt_assert_eq(ret, 0);
+
+	/* Set the fd for udev as non blocking */
+	fd = udev_monitor_get_fd(mon);
+	flags = fcntl(fd, F_GETFL, 0);
+	igt_assert(flags);
+
+	flags |= O_NONBLOCK;
+	igt_assert_neq(fcntl(fd, F_SETFL, flags), -1);
+
+	return mon;
+}
+
+/**
+ * igt_hotplug_detected:
+ * @mon: A udev monitor initialized with #igt_watch_hotplug
+ * @timeout_secs: How long to wait for a hotplug event to occur.
+ *
+ * Assert that a hotplug event was received since we last checked the monitor.
+ *
+ * Returns: true if a sysfs hotplug event was received, false if we timed out
+ */
+bool igt_hotplug_detected(struct udev_monitor *mon, int timeout_secs)
+{
+	struct udev_device *dev;
+	const char *hotplug_val;
+	struct pollfd fd = {
+		.fd = udev_monitor_get_fd(mon),
+		.events = POLLIN
+	};
+	bool hotplug_received = false;
+
+	/* Go through all of the events pending on the udev monitor. Once we
+	 * receive a hotplug, we continue going through the rest of the events
+	 * so that redundant hotplug events don't change the results of future
+	 * checks
+	 */
+	while (!hotplug_received && poll(&fd, 1, timeout_secs * 1000)) {
+		dev = udev_monitor_receive_device(mon);
+
+		hotplug_val = udev_device_get_property_value(dev, "HOTPLUG");
+		if (hotplug_val && atoi(hotplug_val) == 1)
+			hotplug_received = true;
+
+		udev_device_unref(dev);
+	}
+
+	return hotplug_received;
+}
+
+/**
+ * igt_flush_hotplugs:
+ * @mon: A udev monitor initialized with #igt_watch_hotplug
+ *
+ * Get rid of any pending hotplug events
+ */
+void igt_flush_hotplugs(struct udev_monitor *mon)
+{
+	struct udev_device *dev;
+
+	while ((dev = udev_monitor_receive_device(mon)))
+		udev_device_unref(dev);
+}
+
+/**
+ * igt_cleanup_hotplug:
+ *
+ * Cleanup the resources allocated by #igt_watch_hotplug
+ */
+void igt_cleanup_hotplug(struct udev_monitor *mon)
+{
+	struct udev *udev = udev_monitor_get_udev(mon);
+
+	udev_monitor_unref(mon);
+	mon = NULL;
+	udev_unref(udev);
+}
+#endif
+
 /**
  * kmstest_get_vbl_flag:
  * @pipe_id: Pipe to convert to flag representation.
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index 64414a2..53cc900 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -503,5 +503,12 @@ uint32_t kmstest_get_vbl_flag(uint32_t pipe_id);
 const unsigned char* igt_kms_get_base_edid(void);
 const unsigned char* igt_kms_get_alt_edid(void);
 
+#ifdef HAVE_UDEV
+struct udev_monitor *igt_watch_hotplug(void);
+bool igt_hotplug_detected(struct udev_monitor *mon,
+			  int timeout_secs);
+void igt_flush_hotplugs(struct udev_monitor *mon);
+void igt_cleanup_hotplug(struct udev_monitor *mon);
+#endif
 
 #endif /* __IGT_KMS_H__ */
-- 
2.9.3

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