Basic braille screen reader support

This adds a minimalistic braille screen reader support.  This is meant to
be used by blind people e.g.  on boot failures or when / cannot be mounted
etc and thus the userland screen readers can not work.

[akpm@linux-foundation.org: fix exports]
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Jiri Kosina <jikos@jikos.cz>
Cc: Dmitry Torokhov <dtor@mail.ru>
Acked-by: Alan Cox <alan@redhat.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 422 insertions, 0 deletions

diff --git a/drivers/accessibility/Kconfig b/drivers/accessibility/Kconfig
new file mode 100644
index 00000000000..1264c4b9809
--- /dev/null
+++ b/drivers/accessibility/Kconfig
@@ -0,0 +1,23 @@
+menuconfig ACCESSIBILITY
+        bool "Accessibility support"
+        ---help---
+          Enable a submenu where accessibility items may be enabled.
+
+          If unsure, say N.
+
+if ACCESSIBILITY
+config A11Y_BRAILLE_CONSOLE
+        bool "Console on braille device"
+        depends on VT
+        depends on SERIAL_CORE_CONSOLE
+        ---help---
+          Enables console output on a braille device connected to a 8250
+          serial port. For now only the VisioBraille device is supported.
+
+          To actually enable it, you need to pass option
+          console=brl,ttyS0
+          to the kernel. Options are the same as for serial console.
+
+          If unsure, say N.
+
+endif # ACCESSIBILITY
diff --git a/drivers/accessibility/Makefile b/drivers/accessibility/Makefile
new file mode 100644
index 00000000000..72b01a46546
--- /dev/null
+++ b/drivers/accessibility/Makefile
@@ -0,0 +1 @@
+obj-y                           += braille/
diff --git a/drivers/accessibility/braille/Makefile b/drivers/accessibility/braille/Makefile
new file mode 100644
index 00000000000..2e9f16c9134
--- /dev/null
+++ b/drivers/accessibility/braille/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_A11Y_BRAILLE_CONSOLE)              += braille_console.o
diff --git a/drivers/accessibility/braille/braille_console.c b/drivers/accessibility/braille/braille_console.c
new file mode 100644
index 00000000000..0a5f6b2114c
--- /dev/null
+++ b/drivers/accessibility/braille/braille_console.c
@@ -0,0 +1,397 @@
+/*
+ * 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>
+ *
+ * This program is free software ; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation ; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY ; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with the program ; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/autoconf.h>
+#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");
+MODULE_LICENSE("GPL");
+
+/*
+ * Braille device support part.
+ */
+
+/* Emit various sounds */
+static int 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->vc_x - (vc->vc_x % WIDTH);
+        vc_y = vc->vc_y;
+        lastvc_x = vc->vc_x;
+        lastvc_y = vc->vc_y;
+}
+
+/* Maybe the VC cursor moved, if so follow it */
+static void vc_maybe_cursor_moved(struct vc_data *vc)
+{
+        if (vc->vc_x != lastvc_x || vc->vc_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, 1);
+        }
+        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 = vc_kbd_led(kbd_table + fg_console,
+                                                VC_CAPSLOCK);
+                                break;
+                        case KVAL(K_NUM):
+                                on_off = vc_kbd_led(kbd_table + fg_console,
+                                                VC_NUMLOCK);
+                                break;
+                        case KVAL(K_HOLD):
+                                on_off = vc_kbd_led(kbd_table + fg_console,
+                                                VC_SCROLLOCK);
+                                break;
+                        }
+                        if (on_off == 1)
+                                beep(880);
+                        else if (on_off == 0)
+                                beep(440);
+                }
+        }
+        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;
+        return 0;
+}
+
+int braille_unregister_console(struct console *console)
+{
+        if (braille_co != console)
+                return -EINVAL;
+        braille_co = NULL;
+        return 0;
+}
+
+static int __init braille_init(void)
+{
+        register_keyboard_notifier(&keyboard_notifier_block);
+        register_vt_notifier(&vt_notifier_block);
+        return 0;
+}
+
+console_initcall(braille_init);