cdrom: add ->check_events() support
In principle, cdrom just needs to pass through ->check_events() but
CDROM_MEDIA_CHANGED ioctl makes things a bit more complex. Just as
with ->media_changed() support, cdrom code needs to buffer the events
and serve them to ioctl and vfs as requested.
As the code has to deal with both ->check_events() and
->media_changed(), and vfs and ioctl event buffering, this patch adds
check_events caching on top of the existing cdi->mc_flags buffering.
It may be a good idea to deprecate CDROM_MEDIA_CHANGED ioctl and
remove all this mess.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index af13c62..1ea8f8d 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -1348,7 +1348,10 @@
if (!CDROM_CAN(CDC_SELECT_DISC))
return -EDRIVE_CANT_DO_THIS;
- (void) cdi->ops->media_changed(cdi, slot);
+ if (cdi->ops->check_events)
+ cdi->ops->check_events(cdi, 0, slot);
+ else
+ cdi->ops->media_changed(cdi, slot);
if (slot == CDSL_NONE) {
/* set media changed bits, on both queues */
@@ -1392,6 +1395,41 @@
return slot;
}
+/*
+ * As cdrom implements an extra ioctl consumer for media changed
+ * event, it needs to buffer ->check_events() output, such that event
+ * is not lost for both the usual VFS and ioctl paths.
+ * cdi->{vfs|ioctl}_events are used to buffer pending events for each
+ * path.
+ *
+ * XXX: Locking is non-existent. cdi->ops->check_events() can be
+ * called in parallel and buffering fields are accessed without any
+ * exclusion. The original media_changed code had the same problem.
+ * It might be better to simply deprecate CDROM_MEDIA_CHANGED ioctl
+ * and remove this cruft altogether. It doesn't have much usefulness
+ * at this point.
+ */
+static void cdrom_update_events(struct cdrom_device_info *cdi,
+ unsigned int clearing)
+{
+ unsigned int events;
+
+ events = cdi->ops->check_events(cdi, clearing, CDSL_CURRENT);
+ cdi->vfs_events |= events;
+ cdi->ioctl_events |= events;
+}
+
+unsigned int cdrom_check_events(struct cdrom_device_info *cdi,
+ unsigned int clearing)
+{
+ unsigned int events;
+
+ cdrom_update_events(cdi, clearing);
+ events = cdi->vfs_events;
+ cdi->vfs_events = 0;
+ return events;
+}
+
/* We want to make media_changed accessible to the user through an
* ioctl. The main problem now is that we must double-buffer the
* low-level implementation, to assure that the VFS and the user both
@@ -1403,15 +1441,26 @@
{
unsigned int mask = (1 << (queue & 1));
int ret = !!(cdi->mc_flags & mask);
+ bool changed;
if (!CDROM_CAN(CDC_MEDIA_CHANGED))
- return ret;
+ return ret;
+
/* changed since last call? */
- if (cdi->ops->media_changed(cdi, CDSL_CURRENT)) {
+ if (cdi->ops->check_events) {
+ BUG_ON(!queue); /* shouldn't be called from VFS path */
+ cdrom_update_events(cdi, DISK_EVENT_MEDIA_CHANGE);
+ changed = cdi->ioctl_events & DISK_EVENT_MEDIA_CHANGE;
+ cdi->ioctl_events = 0;
+ } else
+ changed = cdi->ops->media_changed(cdi, CDSL_CURRENT);
+
+ if (changed) {
cdi->mc_flags = 0x3; /* set bit on both queues */
ret |= 1;
cdi->media_written = 0;
}
+
cdi->mc_flags &= ~mask; /* clear bit */
return ret;
}