path: root/block/bsg.c

/*
 * bsg.c - block layer implementation of the sg v3 interface
 *
 * Copyright (C) 2004 Jens Axboe <axboe@suse.de> SUSE Labs
 * Copyright (C) 2004 Peter M. Jones <pjones@redhat.com>
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License version 2.  See the file "COPYING" in the main directory of this
 *  archive for more details.
 *
 */
/*
 * TODO
 *	- Should this get merged, block/scsi_ioctl.c will be migrated into
 *	  this file. To keep maintenance down, it's easier to have them
 *	  seperated right now.
 *
 */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/blkdev.h>
#include <linux/poll.h>
#include <linux/cdev.h>
#include <linux/percpu.h>
#include <linux/uio.h>
#include <linux/bsg.h>

#include <scsi/scsi.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/sg.h>

static char bsg_version[] = "block layer sg (bsg) 0.4";

struct bsg_command;

struct bsg_device {
	struct gendisk *disk;
	request_queue_t *queue;
	spinlock_t lock;
	struct list_head busy_list;
	struct list_head done_list;
	struct hlist_node dev_list;
	atomic_t ref_count;
	int minor;
	int queued_cmds;
	int done_cmds;
	unsigned long *cmd_bitmap;
	struct bsg_command *cmd_map;
	wait_queue_head_t wq_done;
	wait_queue_head_t wq_free;
	char name[BDEVNAME_SIZE];
	int max_queue;
	unsigned long flags;
};

enum {
	BSG_F_BLOCK		= 1,
	BSG_F_WRITE_PERM	= 2,
};

/*
 * command allocation bitmap defines
 */
#define BSG_CMDS_PAGE_ORDER	(1)
#define BSG_CMDS_PER_LONG	(sizeof(unsigned long) * 8)
#define BSG_CMDS_MASK		(BSG_CMDS_PER_LONG - 1)
#define BSG_CMDS_BYTES		(PAGE_SIZE * (1 << BSG_CMDS_PAGE_ORDER))
#define BSG_CMDS		(BSG_CMDS_BYTES / sizeof(struct bsg_command))

#undef BSG_DEBUG

#ifdef BSG_DEBUG
#define dprintk(fmt, args...) printk(KERN_ERR "%s: " fmt, __FUNCTION__, ##args)
#else
#define dprintk(fmt, args...)
#endif

#define list_entry_bc(entry)	list_entry((entry), struct bsg_command, list)

/*
 * just for testing
 */
#define BSG_MAJOR	(240)

static DEFINE_MUTEX(bsg_mutex);
static int bsg_device_nr;

#define BSG_LIST_SIZE	(8)
#define bsg_list_idx(minor)	((minor) & (BSG_LIST_SIZE - 1))
static struct hlist_head bsg_device_list[BSG_LIST_SIZE];

static struct class *bsg_class;
static LIST_HEAD(bsg_class_list);

/*
 * our internal command type
 */
struct bsg_command {
	struct bsg_device *bd;
	struct list_head list;
	struct request *rq;
	struct bio *bio;
	int err;
	struct sg_io_v4 hdr;
	struct sg_io_v4 __user *uhdr;
	char sense[SCSI_SENSE_BUFFERSIZE];
};

static void bsg_free_command(struct bsg_command *bc)
{
	struct bsg_device *bd = bc->bd;
	unsigned long bitnr = bc - bd->cmd_map;
	unsigned long flags;

	dprintk("%s: command bit offset %lu\n", bd->name, bitnr);

	spin_lock_irqsave(&bd->lock, flags);
	bd->queued_cmds--;
	__clear_bit(bitnr, bd->cmd_bitmap);
	spin_unlock_irqrestore(&bd->lock, flags);

	wake_up(&bd->wq_free);
}

static struct bsg_command *__bsg_alloc_command(struct bsg_device *bd)
{
	struct bsg_command *bc = NULL;
	unsigned long *map;
	int free_nr;

	spin_lock_irq(&bd->lock);

	if (bd->queued_cmds >= bd->max_queue)
		goto out;

	for (free_nr = 0, map = bd->cmd_bitmap; *map == ~0UL; map++)
		free_nr += BSG_CMDS_PER_LONG;

	BUG_ON(*map == ~0UL);

	bd->queued_cmds++;
	free_nr += ffz(*map);
	__set_bit(free_nr, bd->cmd_bitmap);
	spin_unlock_irq(&bd->lock);

	bc = bd->cmd_map + free_nr;
	memset(bc, 0, sizeof(*bc));
	bc->bd = bd;
	INIT_LIST_HEAD(&bc->list);
	dprintk("%s: returning free cmd %p (bit %d)\n", bd->name, bc, free_nr);
	return bc;
out:
	dprintk("%s: failed (depth %d)\n", bd->name, bd->queued_cmds);
	spin_unlock_irq(&bd->lock);
	return bc;
}

static inline void
bsg_del_done_cmd(struct bsg_device *bd, struct bsg_command *bc)
{
	bd->done_cmds--;
	list_del(&bc->list);
}

static inline void
bsg_add_done_cmd(struct