1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Based on the fbdev code in drivers/video/fbdev/core/fb_cmdline:
4 *
5 *  Copyright (C) 2014 Intel Corp
6 *  Copyright (C) 1994 Martin Schaller
7 *
8 *	2001 - Documented with DocBook
9 *	- Brad Douglas <brad@neruo.com>
10 *
11 * This file is subject to the terms and conditions of the GNU General Public
12 * License.  See the file COPYING in the main directory of this archive
13 * for more details.
14 *
15 * Authors:
16 *    Daniel Vetter <daniel.vetter@ffwll.ch>
17 */
18
19#include <linux/fb.h> /* for FB_MAX */
20#include <linux/init.h>
21
22#include <video/cmdline.h>
23
24/*
25 * FB_MAX is the maximum number of framebuffer devices and also
26 * the maximum number of video= parameters. Although not directly
27 * related to each other, it makes sense to keep it that way.
28 */
29static const char *video_options[FB_MAX] __read_mostly;
30static const char *video_option __read_mostly;
31static int video_of_only __read_mostly;
32
33static const char *__video_get_option_string(const char *name)
34{
35	const char *options = NULL;
36	size_t name_len = 0;
37
38	if (name)
39		name_len = strlen(name);
40
41	if (name_len) {
42		unsigned int i;
43		const char *opt;
44
45		for (i = 0; i < ARRAY_SIZE(video_options); ++i) {
46			if (!video_options[i])
47				continue;
48			if (video_options[i][0] == '\0')
49				continue;
50			opt = video_options[i];
51			if (!strncmp(opt, name, name_len) && opt[name_len] == ':')
52				options = opt + name_len + 1;
53		}
54	}
55
56	/* No match, return global options */
57	if (!options)
58		options = video_option;
59
60	return options;
61}
62
63/**
64 * video_get_options - get kernel boot parameters
65 * @name:	name of the output as it would appear in the boot parameter
66 *		line (video=<name>:<options>)
67 *
68 * Looks up the video= options for the given name. Names are connector
69 * names with DRM, or driver names with fbdev. If no video option for
70 * the name has been specified, the function returns the global video=
71 * setting. A @name of NULL always returns the global video setting.
72 *
73 * Returns:
74 * The string of video options for the given name, or NULL if no video
75 * option has been specified.
76 */
77const char *video_get_options(const char *name)
78{
79	return __video_get_option_string(name);
80}
81EXPORT_SYMBOL(video_get_options);
82
83#if IS_ENABLED(CONFIG_FB_CORE)
84bool __video_get_options(const char *name, const char **options, bool is_of)
85{
86	bool enabled = true;
87	const char *opt = NULL;
88
89	if (video_of_only && !is_of)
90		enabled = false;
91
92	opt = __video_get_option_string(name);
93
94	if (options)
95		*options = opt;
96
97	return enabled;
98}
99EXPORT_SYMBOL(__video_get_options);
100#endif
101
102/*
103 * Process command line options for video adapters. This function is
104 * a __setup and __init function. It only stores the options. Drivers
105 * have to call video_get_options() as necessary.
106 */
107static int __init video_setup(char *options)
108{
109	if (!options || !*options)
110		goto out;
111
112	if (!strncmp(options, "ofonly", 6)) {
113		video_of_only = true;
114		goto out;
115	}
116
117	if (strchr(options, ':')) {
118		/* named */
119		size_t i;
120
121		for (i = 0; i < ARRAY_SIZE(video_options); i++) {
122			if (!video_options[i]) {
123				video_options[i] = options;
124				break;
125			}
126		}
127	} else {
128		/* global */
129		video_option = options;
130	}
131
132out:
133	return 1;
134}
135__setup("video=", video_setup);
136