video/console/dummycon.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  linux/drivers/video/dummycon.c -- A dummy console driver
0004  *
0005  *  To be used if there's no other console driver (e.g. for plain VGA text)
0006  *  available, usually until fbcon takes console over.
0007  */
0008
0009 #include <linux/types.h>
0010 #include <linux/kdev_t.h>
0011 #include <linux/console.h>
0012 #include <linux/vt_kern.h>
0013 #include <linux/screen_info.h>
0014 #include <linux/init.h>
0015 #include <linux/module.h>
0016
0017 /*
0018  *  Dummy console driver
0019  */
0020
0021 #if defined(__arm__)
0022 #define DUMMY_COLUMNS   screen_info.orig_video_cols
0023 #define DUMMY_ROWS  screen_info.orig_video_lines
0024 #else
0025 /* set by Kconfig. Use 80x25 for 640x480 and 160x64 for 1280x1024 */
0026 #define DUMMY_COLUMNS   CONFIG_DUMMY_CONSOLE_COLUMNS
0027 #define DUMMY_ROWS  CONFIG_DUMMY_CONSOLE_ROWS
0028 #endif
0029
0030 #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
0031 /* These are both protected by the console_lock */
0032 static RAW_NOTIFIER_HEAD(dummycon_output_nh);
0033 static bool dummycon_putc_called;
0034
0035 void dummycon_register_output_notifier(struct notifier_block *nb)
0036 {
0037     WARN_CONSOLE_UNLOCKED();
0038
0039     raw_notifier_chain_register(&dummycon_output_nh, nb);
0040
0041     if (dummycon_putc_called)
0042         nb->notifier_call(nb, 0, NULL);
0043 }
0044
0045 void dummycon_unregister_output_notifier(struct notifier_block *nb)
0046 {
0047     WARN_CONSOLE_UNLOCKED();
0048
0049     raw_notifier_chain_unregister(&dummycon_output_nh, nb);
0050 }
0051
0052 static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
0053 {
0054     WARN_CONSOLE_UNLOCKED();
0055
0056     dummycon_putc_called = true;
0057     raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
0058 }
0059
0060 static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
0061                int count, int ypos, int xpos)
0062 {
0063     int i;
0064
0065     if (!dummycon_putc_called) {
0066         /* Ignore erases */
0067         for (i = 0 ; i < count; i++) {
0068             if (s[i] != vc->vc_video_erase_char)
0069                 break;
0070         }
0071         if (i == count)
0072             return;
0073
0074         dummycon_putc_called = true;
0075     }
0076
0077     raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
0078 }
0079
0080 static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
0081 {
0082     /* Redraw, so that we get putc(s) for output done while blanked */
0083     return 1;
0084 }
0085 #else
0086 static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
0087 static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
0088                int count, int ypos, int xpos) { }
0089 static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
0090 {
0091     return 0;
0092 }
0093 #endif
0094
0095 static const char *dummycon_startup(void)
0096 {
0097     return "dummy device";
0098 }
0099
0100 static void dummycon_init(struct vc_data *vc, int init)
0101 {
0102     vc->vc_can_do_color = 1;
0103     if (init) {
0104     vc->vc_cols = DUMMY_COLUMNS;
0105     vc->vc_rows = DUMMY_ROWS;
0106     } else
0107     vc_resize(vc, DUMMY_COLUMNS, DUMMY_ROWS);
0108 }
0109
0110 static void dummycon_deinit(struct vc_data *vc) { }
0111 static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
0112                int width) { }
0113 static void dummycon_cursor(struct vc_data *vc, int mode) { }
0114
0115 static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
0116                 unsigned int bottom, enum con_scroll dir,
0117                 unsigned int lines)
0118 {
0119     return false;
0120 }
0121
0122 static int dummycon_switch(struct vc_data *vc)
0123 {
0124     return 0;
0125 }
0126
0127 /*
0128  *  The console `switch' structure for the dummy console
0129  *
0130  *  Most of the operations are dummies.
0131  */
0132
0133 const struct consw dummy_con = {
0134     .owner =        THIS_MODULE,
0135     .con_startup =  dummycon_startup,
0136     .con_init =     dummycon_init,
0137     .con_deinit =   dummycon_deinit,
0138     .con_clear =    dummycon_clear,
0139     .con_putc =     dummycon_putc,
0140     .con_putcs =    dummycon_putcs,
0141     .con_cursor =   dummycon_cursor,
0142     .con_scroll =   dummycon_scroll,
0143     .con_switch =   dummycon_switch,
0144     .con_blank =    dummycon_blank,
0145 };
0146 EXPORT_SYMBOL_GPL(dummy_con);