// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Minimalistic braille device kernel support.
 *
 * By default, shows console messages on the braille device.
 * Pressing Insert switches to VC browsing.
 *
 *  Copyright (C) Samuel Thibault <samuel.thibault@ens-lyon.org>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/console.h>
#include <linux/notifier.h>

#include <linux/selection.h>
#include <linux/vt_kern.h>
#include <linux/consolemap.h>

#include <linux/keyboard.h>
#include <linux/kbd_kern.h>
#include <linux/input.h>

MODULE_AUTHOR("samuel.thibault@ens-lyon.org");
MODULE_DESCRIPTION("braille device");

/*
 * Braille device support part.
 */

/* Emit various sounds */
static bool sound;
module_param(sound, bool, 0);
MODULE_PARM_DESC(sound, "emit sounds");

static void beep(unsigned int freq)
{
        if (sound)
                kd_mksound(freq, HZ/10);
}

/* mini console */
#define WIDTH 40
#define BRAILLE_KEY KEY_INSERT
static u16 console_buf[WIDTH];
static int console_cursor;

/* mini view of VC */
static int vc_x, vc_y, lastvc_x, lastvc_y;

/* show console ? (or show VC) */
static int console_show = 1;
/* pending newline ? */
static int console_newline = 1;
static int lastVC = -1;

static struct console *braille_co;

/* Very VisioBraille-specific */
static void braille_write(u16 *buf)
{
        static u16 lastwrite[WIDTH];
        unsigned char data[1 + 1 + 2*WIDTH + 2 + 1], csum = 0, *c;
        u16 out;
        int i;

        if (!braille_co)
                return;

        if (!memcmp(lastwrite, buf, WIDTH * sizeof(*buf)))
                return;
        memcpy(lastwrite, buf, WIDTH * sizeof(*buf));

#define SOH 1
#define STX 2
#define ETX 2
#define EOT 4
#define ENQ 5
        data[0] = STX;
        data[1] = '>';
        csum ^= '>';
        c = &data[2];
        for (i = 0; i < WIDTH; i++) {
                out = buf[i];
                if (out >= 0x100)
                        out = '?';
                else if (out == 0x00)
                        out = ' ';
                csum ^= out;
                if (out <= 0x05) {
                        *c++ = SOH;
                        out |= 0x40;
                }
                *c++ = out;
        }

        if (csum <= 0x05) {
                *c++ = SOH;
                csum |= 0x40;
        }
        *c++ = csum;
        *c++ = ETX;

        braille_co->write(braille_co, data, c - data);
}

/* Follow the VC cursor*/
static void vc_follow_cursor(struct vc_data *vc)
{
        vc_x = vc->state.x - (vc->state.x % WIDTH);
        vc_y = vc->state.y;
        lastvc_x = vc->state.x;
        lastvc_y = vc->state.y;
}

/* Maybe the VC cursor moved, if so follow it */
static void vc_maybe_cursor_moved(struct vc_data *vc)
{
        if (vc->state.x != lastvc_x || vc->state.y != lastvc_y)
                vc_follow_cursor(vc);
}

/* Show portion of VC at vc_x, vc_y */
static void vc_refresh(struct vc_data *vc)
{
        u16 buf[WIDTH];
        int i;

        for (i = 0; i < WIDTH; i++) {
                u16 glyph = screen_glyph(vc,
                                2 * (vc_x + i) + vc_y * vc->vc_size_row);
                buf[i] = inverse_translate(vc, glyph, true);
        }
        braille_write(buf);
}

/*
 * Link to keyboard
 */

static int keyboard_notifier_call(struct notifier_block *blk,
                                  unsigned long code, void *_param)
{
        struct keyboard_notifier_param *param = _param;
        struct vc_data *vc = param->vc;
        int ret = NOTIFY_OK;

        if (!param->down)
                return ret;

        switch (code) {
        case KBD_KEYCODE:
                if (console_show) {
                        if (param->value == BRAILLE_KEY) {
                                console_show = 0;
                                beep(880);
                                vc_maybe_cursor_moved(vc);
                                vc_refresh(vc);
                                ret = NOTIFY_STOP;
                        }
                } else {
                        ret = NOTIFY_STOP;
                        switch (param->value) {
                        case KEY_INSERT:
                                beep(440);
                                console_show = 1;
                                lastVC = -1;
                                braille_write(console_buf);
                                break;
                        case KEY_LEFT:
                                if (vc_x > 0) {
                                        vc_x -= WIDTH;
                                        if (vc_x < 0)
                                                vc_x = 0;
                                } else if (vc_y >= 1) {
                                        beep(880);
                                        vc_y--;
                                        vc_x = vc->vc_cols-WIDTH;
                                } else
                                        beep(220);
                                break;
                        case KEY_RIGHT:
                                if (vc_x + WIDTH < vc->vc_cols) {
                                        vc_x += WIDTH;
                                } else if (vc_y + 1 < vc->vc_rows) {
                                        beep(880);
                                        vc_y++;
                                        vc_x = 0;
                                } else
                                        beep(220);
                                break;
                        case KEY_DOWN:
                                if (vc_y + 1 < vc->vc_rows)
                                        vc_y++;
                                else
                                        beep(220);
                                break;
                        case KEY_UP:
                                if (vc_y >= 1)
                                        vc_y--;
                                else
                                        beep(220);
                                break;
                        case KEY_HOME:
                                vc_follow_cursor(vc);
                                break;
                        case KEY_PAGEUP:
                                vc_x = 0;
                                vc_y = 0;
                                break;
                        case KEY_PAGEDOWN:
                                vc_x = 0;
                                vc_y = vc->vc_rows-1;
                                break;
                        default:
                                ret = NOTIFY_OK;
                                break;
                        }
                        if (ret == NOTIFY_STOP)
                                vc_refresh(vc);
                }
                break;
        case KBD_POST_KEYSYM:
        {
                unsigned char type = KTYP(param->value) - 0xf0;

                if (type == KT_SPEC) {
                        unsigned char val = KVAL(param->value);
                        int on_off = -1;

                        switch (val) {
                        case KVAL(K_CAPS):
                                on_off = vt_get_leds(fg_console, VC_CAPSLOCK);
                                break;
                        case KVAL(K_NUM):
                                on_off = vt_get_leds(fg_console, VC_NUMLOCK);
                                break;
                        case KVAL(K_HOLD):
                                on_off = vt_get_leds(fg_console, VC_SCROLLOCK);
                                break;
                        }
                        if (on_off == 1)
                                beep(880);
                        else if (on_off == 0)
                                beep(440);
                }
        }
                break;
        case KBD_UNBOUND_KEYCODE:
        case KBD_UNICODE:
        case KBD_KEYSYM:
                /* Unused */
                break;
        }
        return ret;
}

static struct notifier_block keyboard_notifier_block = {
        .notifier_call = keyboard_notifier_call,
};

static int vt_notifier_call(struct notifier_block *blk,
                            unsigned long code, void *_param)
{
        struct vt_notifier_param *param = _param;
        struct vc_data *vc = param->vc;

        switch (code) {
        case VT_ALLOCATE:
                break;
        case VT_DEALLOCATE:
                break;
        case VT_WRITE:
        {
                unsigned char c = param->c;

                if (vc->vc_num != fg_console)
                        break;
                switch (c) {
                case '\b':
                case 127:
                        if (console_cursor > 0) {
                                console_cursor--;
                                console_buf[console_cursor] = ' ';
                        }
                        break;
                case '\n':
                case '\v':
                case '\f':
                case '\r':
                        console_newline = 1;
                        break;
                case '\t':
                        c = ' ';
                        fallthrough;
                default:
                        if (c < 32)
                                /* Ignore other control sequences */
                                break;
                        if (console_newline) {
                                memset(console_buf, 0, sizeof(console_buf));
                                console_cursor = 0;
                                console_newline = 0;
                        }
                        if (console_cursor == WIDTH)
                                memmove(console_buf, &console_buf[1],
                                        (WIDTH-1) * sizeof(*console_buf));
                        else
                                console_cursor++;
                        console_buf[console_cursor-1] = c;
                        break;
                }
                if (console_show)
                        braille_write(console_buf);
                else {
                        vc_maybe_cursor_moved(vc);
                        vc_refresh(vc);
                }
                break;
        }
        case VT_UPDATE:
                /* Maybe a VT switch, flush */
                if (console_show) {
                        if (vc->vc_num != lastVC) {
                                lastVC = vc->vc_num;
                                memset(console_buf, 0, sizeof(console_buf));
                                console_cursor = 0;
                                braille_write(console_buf);
                        }
                } else {
                        vc_maybe_cursor_moved(vc);
                        vc_refresh(vc);
                }
                break;
        }
        return NOTIFY_OK;
}

static struct notifier_block vt_notifier_block = {
        .notifier_call = vt_notifier_call,
};

/*
 * Called from printk.c when console=brl is given
 */

int braille_register_console(struct console *console, int index,
                char *console_options, char *braille_options)
{
        int ret;

        if (!console_options)
                /* Only support VisioBraille for now */
                console_options = "57600o8";
        if (braille_co)
                return -ENODEV;
        if (console->setup) {
                ret = console->setup(console, console_options);
                if (ret != 0)
                        return ret;
        }
        console->flags |= CON_ENABLED;
        console->index = index;
        braille_co = console;
        register_keyboard_notifier(&keyboard_notifier_block);
        register_vt_notifier(&vt_notifier_block);
        return 1;
}

int braille_unregister_console(struct console *console)
{
        if (braille_co != console)
                return -EINVAL;
        unregister_keyboard_notifier(&keyboard_notifier_block);
        unregister_vt_notifier(&vt_notifier_block);
        braille_co = NULL;
        return 1;
}