xref: /freebsd/sys/compat/linuxkpi/common/src/linux_cmdline.c (revision 87b759f0fa1f7554d50ce640c40138512bbded44)
1 /*-
2  * Copyright (c) 2022 Beckhoff Automation GmbH & Co. KG
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  * 1. Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  * 2. Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  *
13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23  * SUCH DAMAGE.
24  *
25  */
26 
27 #include <sys/param.h>
28 #include <sys/systm.h>
29 
30 #include <video/cmdline.h>
31 
32 const char *
33 video_get_options(const char *connector_name)
34 {
35 	char tunable[64];
36 	const char *options;
37 
38 	/*
39 	 * A user may use loader tunables to set a specific mode for the
40 	 * console. Tunables are read in the following order:
41 	 *     1. kern.vt.fb.modes.$connector_name
42 	 *     2. kern.vt.fb.default_mode
43 	 *
44 	 * Example of a mode specific to the LVDS connector:
45 	 *     kern.vt.fb.modes.LVDS="1024x768"
46 	 *
47 	 * Example of a mode applied to all connectors not having a
48 	 * connector-specific mode:
49 	 *     kern.vt.fb.default_mode="640x480"
50 	 */
51 	snprintf(tunable, sizeof(tunable), "kern.vt.fb.modes.%s",
52 	    connector_name);
53 	if (bootverbose) {
54 		printf("[drm] Connector %s: get mode from tunables:\n", connector_name);
55 		printf("[drm]  - %s\n", tunable);
56 		printf("[drm]  - kern.vt.fb.default_mode\n");
57 	}
58 	options = kern_getenv(tunable);
59 	if (options == NULL)
60 		options = kern_getenv("kern.vt.fb.default_mode");
61 
62 	return (options);
63 }
64