From 99024d17b1d5672668fda412148b87d8cf33cedf Mon Sep 17 00:00:00 2001
From: Martin Pitt <martin.pitt@ubuntu.com>
Date: Fri, 1 Apr 2011 19:06:59 +0200
Subject: [PATCH 1/4] Use in-kernel media probing when available

Check whether the kernel supports in-kernel media polling (since 2.6.38,
https://lkml.org/lkml/2010/12/8/299), and use it instead of user-space polling.

Preparation for bug #34710.
---
 src/device-private.c |   22 +++++++++++++++++
 src/device-private.h |    6 +++++
 src/poller.c         |   62 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+), 0 deletions(-)

diff --git a/src/device-private.c b/src/device-private.c
index 22a0d35..d4ec6c5 100644
--- a/src/device-private.c
+++ b/src/device-private.c
@@ -187,6 +187,28 @@ device_set_job_percentage (Device *device,
 }
 
 void
+device_set_supports_media_change_event (Device *device,
+                           gboolean value)
+{
+  if (G_UNLIKELY (device->priv->supports_media_change_event != value))
+    {
+      device->priv->supports_media_change_event = value;
+      emit_changed (device, "supports_media_change_event");
+    }
+}
+
+void
+device_set_supports_eject_request_event (Device *device,
+                           gboolean value)
+{
+  if (G_UNLIKELY (device->priv->supports_eject_request_event != value))
+    {
+      device->priv->supports_eject_request_event = value;
+      emit_changed (device, "supports_eject_request_event");
+    }
+}
+
+void
 device_set_device_file (Device *device,
                         const gchar *value)
 {
diff --git a/src/device-private.h b/src/device-private.h
index a6db7f2..01149e5 100644
--- a/src/device-private.h
+++ b/src/device-private.h
@@ -59,6 +59,9 @@ struct DevicePrivate
   gboolean job_is_cancellable;
   double job_percentage;
 
+  gboolean supports_media_change_event;
+  gboolean supports_eject_request_event;
+
   guint linux_md_poll_timeout_id;
 
   /* A list of current polling inhibitors (Inhibitor objects) */
@@ -250,6 +253,9 @@ void device_set_job_initiated_by_uid (Device *device, guint value);
 void device_set_job_is_cancellable (Device *device, gboolean value);
 void device_set_job_percentage (Device *device, gdouble value);
 
+void device_set_supports_media_change_event (Device *device, gboolean value);
+void device_set_supports_eject_request_event (Device *device, gboolean value);
+
 void device_set_device_detection_time (Device *device, guint64 value);
 void device_set_device_media_detection_time (Device *device, guint64 value);
 void device_set_device_file (Device *device, const gchar *value);
diff --git a/src/poller.c b/src/poller.c
index 9517b5d..1bf265b 100644
--- a/src/poller.c
+++ b/src/poller.c
@@ -31,6 +31,7 @@
 #include <fcntl.h>
 #include <string.h>
 #include <errno.h>
+#include <gudev/gudev.h>
 
 #include "poller.h"
 #include "device.h"
@@ -304,6 +305,64 @@ poller_setup (int argc,
 
 /* ---------------------------------------------------------------------------------------------------- */
 
+static gboolean
+check_in_kernel_polling (Device* d)
+{
+  const char *supported_events;
+  gboolean ret = FALSE;
+
+  /* only check once */
+  if (d->priv->supports_media_change_event)
+    return TRUE;
+
+  supported_events = g_udev_device_get_sysfs_attr (d->priv->d, "events");
+
+#ifdef POLL_SHOW_DEBUG
+  g_print("**** POLLER (%d): Supported events for %s: %s\n", getpid (), d->priv->device_file, supported_events);
+#endif
+
+  if (strstr (supported_events, "eject_request"))
+    device_set_supports_eject_request_event (d, TRUE);
+
+  if (strstr (supported_events, "media_change"))
+    {
+      /* enable in-kernel polling */
+      if (g_udev_device_get_sysfs_attr_as_int (d->priv->d, "events_poll_msecs") <= 0)
+	{
+	  int fd;
+	  char *attr = g_build_filename (d->priv->native_path, "events_poll_msecs", NULL);
+	  const char* poll_time = "2000";
+	  size_t poll_time_size = strlen (poll_time);
+
+	  fd = open (attr, O_WRONLY);
+	  g_free (attr);
+	  if (fd > 0)
+	    {
+	      if (write (fd, poll_time, poll_time_size) == (ssize_t) poll_time_size)
+		{
+#ifdef POLL_SHOW_DEBUG
+		  g_print("**** POLLER (%d): Successfully enabled in-kernel polling for %s\n", getpid (), d->priv->device_file);
+#endif
+		  device_set_supports_media_change_event (d, TRUE);
+		  ret = TRUE;
+		}
+	      close (fd);
+	    }
+	} else {
+	  /* there is already a poll time set */
+#ifdef POLL_SHOW_DEBUG
+	    g_print("**** POLLER (%d): In-kernel polling for %s already enabled\n", getpid (), d->priv->device_file);
+#endif
+	  device_set_supports_media_change_event (d, TRUE);
+	  ret = TRUE;
+	}
+    }
+
+  return ret;
+}
+
+/* ---------------------------------------------------------------------------------------------------- */
+
 void
 poller_set_devices (GList *devices)
 {
@@ -320,6 +379,9 @@ poller_set_devices (GList *devices)
     {
       Device *device = DEVICE (l->data);
 
+      if (check_in_kernel_polling (device))
+	continue;
+
       device_array[n++] = device->priv->device_file;
     }
 
-- 
1.7.4.1