/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_TTY_BUFFER_H
#define _LINUX_TTY_BUFFER_H

#include <linux/atomic.h>
#include <linux/llist.h>
#include <linux/mutex.h>
#include <linux/workqueue.h>

struct tty_buffer {
    union {
        struct tty_buffer *next;
        struct llist_node free;
    };
    unsigned int used;
    unsigned int size;
    unsigned int commit;
    unsigned int lookahead;        /* Lazy update on recv, can become less than "read" */
    unsigned int read;
    bool flags;
    /* Data points here */
    u8 data[] __aligned(sizeof(unsigned long));
};

static inline u8 *char_buf_ptr(struct tty_buffer *b, unsigned int ofs)
{
    return b->data + ofs;
}

static inline u8 *flag_buf_ptr(struct tty_buffer *b, unsigned int ofs)
{
    return char_buf_ptr(b, ofs) + b->size;
}

struct tty_bufhead {
    struct tty_buffer *head;    /* Queue head */
    struct work_struct work;
    struct mutex       lock;
    atomic_t       priority;
    struct tty_buffer sentinel;
    struct llist_head free;        /* Free queue head */
    atomic_t       mem_used;    /* In-use buffers excluding free list */
    int           mem_limit;
    struct tty_buffer *tail;    /* Active buffer */
};

/*
 * When a break, frame error, or parity error happens, these codes are
 * stuffed into the flags buffer.
 */
#define TTY_NORMAL    0
#define TTY_BREAK    1
#define TTY_FRAME    2
#define TTY_PARITY    3
#define TTY_OVERRUN    4

#endif