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cdrom: add ->check_events() support

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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>
This commit is contained in:
Tejun Heo 2010-12-08 20:57:38 +01:00 committed by Jens Axboe
parent 77ea887e43
commit 2d9217296b
2 changed files with 58 additions and 3 deletions
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55
drivers/cdrom/cdrom.c
View File

@ -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;
}

6
include/linux/cdrom.h
View File

@ -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);