/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
#ifndef _UAPI_LINUX_IOPRIO_H
#define _UAPI_LINUX_IOPRIO_H

#include <linux/stddef.h>
#include <linux/types.h>

/*
 * Gives us 8 prio classes with 13-bits of data for each class
 */
#define IOPRIO_CLASS_SHIFT      13
#define IOPRIO_NR_CLASSES       8
#define IOPRIO_CLASS_MASK       (IOPRIO_NR_CLASSES - 1)
#define IOPRIO_PRIO_MASK        ((1UL << IOPRIO_CLASS_SHIFT) - 1)

#define IOPRIO_PRIO_CLASS(ioprio)       \
        (((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
#define IOPRIO_PRIO_DATA(ioprio)        ((ioprio) & IOPRIO_PRIO_MASK)

/*
 * These are the io priority classes as implemented by the BFQ and mq-deadline
 * schedulers. RT is the realtime class, it always gets premium service. For
 * ATA disks supporting NCQ IO priority, RT class IOs will be processed using
 * high priority NCQ commands. BE is the best-effort scheduling class, the
 * default for any process. IDLE is the idle scheduling class, it is only
 * served when no one else is using the disk.
 */
enum {
        IOPRIO_CLASS_NONE       = 0,
        IOPRIO_CLASS_RT         = 1,
        IOPRIO_CLASS_BE         = 2,
        IOPRIO_CLASS_IDLE       = 3,

        /* Special class to indicate an invalid ioprio value */
        IOPRIO_CLASS_INVALID    = 7,
};

/*
 * The RT and BE priority classes both support up to 8 priority levels that
 * can be specified using the lower 3-bits of the priority data.
 */
#define IOPRIO_LEVEL_NR_BITS            3
#define IOPRIO_NR_LEVELS                (1 << IOPRIO_LEVEL_NR_BITS)
#define IOPRIO_LEVEL_MASK               (IOPRIO_NR_LEVELS - 1)
#define IOPRIO_PRIO_LEVEL(ioprio)       ((ioprio) & IOPRIO_LEVEL_MASK)

#define IOPRIO_BE_NR                    IOPRIO_NR_LEVELS

/*
 * Possible values for the "which" argument of the ioprio_get() and
 * ioprio_set() system calls (see "man ioprio_set").
 */
enum {
        IOPRIO_WHO_PROCESS = 1,
        IOPRIO_WHO_PGRP,
        IOPRIO_WHO_USER,
};

/*
 * Fallback BE class priority level.
 */
#define IOPRIO_NORM     4
#define IOPRIO_BE_NORM  IOPRIO_NORM

/*
 * The 10 bits between the priority class and the priority level are used to
 * optionally define I/O hints for any combination of I/O priority class and
 * level. Depending on the kernel configuration, I/O scheduler being used and
 * the target I/O device being used, hints can influence how I/Os are processed
 * without affecting the I/O scheduling ordering defined by the I/O priority
 * class and level.
 */
#define IOPRIO_HINT_SHIFT               IOPRIO_LEVEL_NR_BITS
#define IOPRIO_HINT_NR_BITS             10
#define IOPRIO_NR_HINTS                 (1 << IOPRIO_HINT_NR_BITS)
#define IOPRIO_HINT_MASK                (IOPRIO_NR_HINTS - 1)
#define IOPRIO_PRIO_HINT(ioprio)        \
        (((ioprio) >> IOPRIO_HINT_SHIFT) & IOPRIO_HINT_MASK)

/*
 * I/O hints.
 */
enum {
        /* No hint */
        IOPRIO_HINT_NONE = 0,

        /*
         * Device command duration limits: indicate to the device a desired
         * duration limit for the commands that will be used to process an I/O.
         * These will currently only be effective for SCSI and ATA devices that
         * support the command duration limits feature. If this feature is
         * enabled, then the commands issued to the device to process an I/O with
         * one of these hints set will have the duration limit index (dld field)
         * set to the value of the hint.
         */
        IOPRIO_HINT_DEV_DURATION_LIMIT_1 = 1,
        IOPRIO_HINT_DEV_DURATION_LIMIT_2 = 2,
        IOPRIO_HINT_DEV_DURATION_LIMIT_3 = 3,
        IOPRIO_HINT_DEV_DURATION_LIMIT_4 = 4,
        IOPRIO_HINT_DEV_DURATION_LIMIT_5 = 5,
        IOPRIO_HINT_DEV_DURATION_LIMIT_6 = 6,
        IOPRIO_HINT_DEV_DURATION_LIMIT_7 = 7,
};

#define IOPRIO_BAD_VALUE(val, max) ((val) < 0 || (val) >= (max))

/*
 * Return an I/O priority value based on a class, a level and a hint.
 */
static __always_inline __u16 ioprio_value(int prioclass, int priolevel,
                                          int priohint)
{
        if (IOPRIO_BAD_VALUE(prioclass, IOPRIO_NR_CLASSES) ||
            IOPRIO_BAD_VALUE(priolevel, IOPRIO_NR_LEVELS) ||
            IOPRIO_BAD_VALUE(priohint, IOPRIO_NR_HINTS))
                return IOPRIO_CLASS_INVALID << IOPRIO_CLASS_SHIFT;

        return (prioclass << IOPRIO_CLASS_SHIFT) |
                (priohint << IOPRIO_HINT_SHIFT) | priolevel;
}

#define IOPRIO_PRIO_VALUE(prioclass, priolevel)                 \
        ioprio_value(prioclass, priolevel, IOPRIO_HINT_NONE)
#define IOPRIO_PRIO_VALUE_HINT(prioclass, priolevel, priohint)  \
        ioprio_value(prioclass, priolevel, priohint)

#endif /* _UAPI_LINUX_IOPRIO_H */