// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2010 Werner Fink, Jiri Slaby
 */

#include <linux/console.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/tty_driver.h>

/*
 * This is handler for /proc/consoles
 */
static int show_console_dev(struct seq_file *m, void *v)
{
        static const struct {
                short flag;
                char name;
        } con_flags[] = {
                { CON_ENABLED,          'E' },
                { CON_CONSDEV,          'C' },
                { CON_BOOT,             'B' },
                { CON_NBCON,            'N' },
                { CON_PRINTBUFFER,      'p' },
                { CON_BRL,              'b' },
                { CON_ANYTIME,          'a' },
        };
        char flags[ARRAY_SIZE(con_flags) + 1];
        struct console *con = v;
        unsigned int a;
        dev_t dev = 0;

        if (con->device) {
                const struct tty_driver *driver;
                int index;

                /*
                 * Take console_lock to serialize device() callback with
                 * other console operations. For example, fg_console is
                 * modified under console_lock when switching vt.
                 */
                console_lock();
                driver = con->device(con, &index);
                console_unlock();

                if (driver) {
                        dev = MKDEV(driver->major, driver->minor_start);
                        dev += index;
                }
        }

        for (a = 0; a < ARRAY_SIZE(con_flags); a++)
                flags[a] = (con->flags & con_flags[a].flag) ?
                        con_flags[a].name : ' ';
        flags[a] = 0;

        seq_setwidth(m, 21 - 1);
        seq_printf(m, "%s%d", con->name, con->index);
        seq_pad(m, ' ');
        seq_printf(m, "%c%c%c (%s)", con->read ? 'R' : '-',
                   ((con->flags & CON_NBCON) || con->write) ? 'W' : '-',
                   con->unblank ? 'U' : '-', flags);
        if (dev)
                seq_printf(m, " %4d:%d", MAJOR(dev), MINOR(dev));

        seq_putc(m, '\n');
        return 0;
}

static void *c_start(struct seq_file *m, loff_t *pos)
        __acquires(&console_mutex)
{
        struct console *con;
        loff_t off = 0;

        /*
         * Hold the console_list_lock to guarantee safe traversal of the
         * console list. SRCU cannot be used because there is no
         * place to store the SRCU cookie.
         */
        console_list_lock();
        for_each_console(con)
                if (off++ == *pos)
                        break;

        return con;
}

static void *c_next(struct seq_file *m, void *v, loff_t *pos)
{
        struct console *con = v;

        ++*pos;
        return hlist_entry_safe(con->node.next, struct console, node);
}

static void c_stop(struct seq_file *m, void *v)
        __releases(&console_mutex)
{
        console_list_unlock();
}

static const struct seq_operations consoles_op = {
        .start  = c_start,
        .next   = c_next,
        .stop   = c_stop,
        .show   = show_console_dev
};

static int __init proc_consoles_init(void)
{
        proc_create_seq("consoles", 0, NULL, &consoles_op);
        return 0;
}
fs_initcall(proc_consoles_init);