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Commit 2d921729 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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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: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 77ea887e

drivers/cdrom/cdrom.c

+52 −3
Original line number Diff line number Diff line
@@ -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;



	/* 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;

}

include/linux/cdrom.h

+6 −0
Original line number Diff line number Diff line
@@ -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);