/* 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