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Subject[PATCH 4/7] cdrom: add ->check_events() support
Date
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. It may be a good idea
to deprecate CDROM_MEDIA_CHANGED ioctl in the long run.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
drivers/cdrom/cdrom.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++--
include/linux/cdrom.h | 6 +++++
2 files changed, 58 insertions(+), 3 deletions(-)
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 @@ static int cdrom_select_disc(struct cdrom_device_info *cdi, int slot)
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 @@ static int cdrom_select_disc(struct cdrom_device_info *cdi, int slot)
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 @@ int media_changed(struct cdrom_device_info *cdi, int queue)
{
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;
}
diff --git a/include/linux/cdrom.h b/include/linux/cdrom.h
index 78e9047..35eae4b 100644
--- a/include/linux/cdrom.h
+++ b/include/linux/cdrom.h
@@ -946,6 +946,8 @@ struct cdrom_device_info {
/* device-related storage */
unsigned int options : 30; /* options flags */
unsigned mc_flags : 2; /* media change buffer flags */
+ unsigned int vfs_events; /* cached events for vfs path */
+ unsigned int ioctl_events; /* cached events for ioctl path */
int use_count; /* number of times device opened */
char name[20]; /* name of the device type */
/* per-device flags */
@@ -965,6 +967,8 @@ struct cdrom_device_ops {
int (*open) (struct cdrom_device_info *, int);
void (*release) (struct cdrom_device_info *);
int (*drive_status) (struct cdrom_device_info *, int);
+ unsigned int (*check_events) (struct cdrom_device_info *cdi,
+ unsigned int clearing, int slot);
int (*media_changed) (struct cdrom_device_info *, int);
int (*tray_move) (struct cdrom_device_info *, int);
int (*lock_door) (struct cdrom_device_info *, int);
@@ -993,6 +997,8 @@ extern int cdrom_open(struct cdrom_device_info *cdi, struct block_device *bdev,
extern void cdrom_release(struct cdrom_device_info *cdi, fmode_t mode);
extern int cdrom_ioctl(struct cdrom_device_info *cdi, struct block_device *bdev,
fmode_t mode, unsigned int cmd, unsigned long arg);
+extern unsigned int cdrom_check_events(struct cdrom_device_info *cdi,
+ unsigned int clearing);
extern int cdrom_media_changed(struct cdrom_device_info *);

extern int register_cdrom(struct cdrom_device_info *cdi);
--
1.7.1


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