From 03d8ee1a95a49d386b564054858001143300192a 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.

This can be disabled by setting ENV{UDISKS_DISABLE_KERNEL_POLLING}="1" in an
udisks rule.

Preparation for bug #34710.
---
 src/device-private.h |    5 +++
 src/poller.c         |   78 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 0 deletions(-)

diff --git a/src/device-private.h b/src/device-private.h
index a6db7f2..160ff65 100644
--- a/src/device-private.h
+++ b/src/device-private.h
@@ -59,6 +59,11 @@ struct DevicePrivate
   gboolean job_is_cancellable;
   double job_percentage;
 
+  gboolean checked_in_kernel_polling_support;
+  gboolean using_in_kernel_polling;
+  gboolean supports_media_change_event;
+  gboolean supports_eject_request_event;
+
   guint linux_md_poll_timeout_id;
 
   /* A list of current polling inhibitors (Inhibitor objects) */
diff --git a/src/poller.c b/src/poller.c
index 9517b5d..f518617 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 +305,80 @@ poller_setup (int argc,
 
 /* ---------------------------------------------------------------------------------------------------- */
 
+static void
+enable_in_kernel_polling (Device* d)
+{
+  /* enable in-kernel polling */
+  if (g_udev_device_get_sysfs_attr_as_int (d->priv->d, "events_poll_msecs") <= 0)
+    {
+      int fd;
+      gchar *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
+          }
+          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
+    }
+}
+
+static gboolean
+check_and_enable_in_kernel_polling (Device* d)
+{
+  /* only check once */
+  if (!d->priv->checked_in_kernel_polling_support)
+    {
+      const char *supported_events;
+      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"))
+	d->priv->supports_eject_request_event = TRUE;
+
+      if (strstr (supported_events, "media_change"))
+	{
+      	  d->priv->supports_media_change_event = TRUE;
+
+	  /* Allow udev rules to disable in-kernel polling */
+	  if (g_udev_device_get_property_as_boolean (d->priv->d, "UDISKS_DISABLE_KERNEL_POLLING"))
+	    {
+	      d->priv->using_in_kernel_polling = FALSE;
+#ifdef POLL_SHOW_DEBUG
+	      g_print("**** POLLER (%d): In-kernel polling for %s disabled with UDISKS_DISABLE_KERNEL_POLLING\n", getpid (), d->priv->device_file);
+#endif
+	    }
+	  else
+	    {
+	      d->priv->using_in_kernel_polling = TRUE;
+	      enable_in_kernel_polling (d);
+	    }
+	}
+
+      d->priv->checked_in_kernel_polling_support = TRUE;
+    }
+
+  return d->priv->supports_media_change_event && d->priv->using_in_kernel_polling;
+}
+
+/* ---------------------------------------------------------------------------------------------------- */
+
 void
 poller_set_devices (GList *devices)
 {
@@ -320,6 +395,9 @@ poller_set_devices (GList *devices)
     {
       Device *device = DEVICE (l->data);
 
+      if (check_and_enable_in_kernel_polling (device))
+	continue;
+
       device_array[n++] = device->priv->device_file;
     }
 
-- 
1.7.5.4