/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 *	Author: David B. Golub, Carnegie Mellon University
 *	Date: 	7/89
 *
 * 	Block IO driven from generic kernel IO interface.
 */
#include <mach/kern_return.h>

#include <device/param.h>
#include <device/device_types.h>
#include <device/io_req.h>
#include <device/ds_routines.h>



io_return_t block_io(
	void			(*strat)(),
	void			(*max_count)(),
	io_req_t		ior)
{
	kern_return_t		rc;
	boolean_t		wait = FALSE;

	/*
	 * Make sure the size is not too large by letting max_count
	 * change io_count.  If we are doing a write, then io_alloc_size
	 * preserves the original io_count.
	 */
	(*max_count)(ior);

	/*
	 * If reading, allocate memory.  If writing, wire
	 * down the incoming memory.
	 */
	if (ior->io_op & IO_READ)
	    rc = device_read_alloc(ior, (vm_size_t)ior->io_count);
	else
	    rc = device_write_get(ior, &wait);

	if (rc != KERN_SUCCESS)
	    return (rc);

	/*
	 * Queue the operation for the device.
	 */
	(*strat)(ior);

	/*
	 * The io is now queued.  Wait for it if needed.
	 */
	if (wait) {
		iowait(ior);
		return(D_SUCCESS);
	}

	return (D_IO_QUEUED);
}

/*
 * 'standard' max_count routine.  VM continuations mean that this
 * code can cope with arbitrarily-sized write operations (they won't be
 * atomic, but any caller that cares will do the op synchronously).
 */
#define MAX_PHYS        (256 * 1024)

void minphys(io_req_t ior)
{
	if ((ior->io_op & (IO_WRITE | IO_READ | IO_OPEN)) == IO_WRITE)
	    return;

        if (ior->io_count > MAX_PHYS)
            ior->io_count = MAX_PHYS;
}

/*
 * Dummy routine placed in device switch entries to indicate that
 * block device may be mapped.
 */
vm_offset_t block_io_mmap(dev_t dev, vm_offset_t off, int prot)
{
	return (0);
}