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
 83bool __video_get_options(const char *name, const char **options, bool is_of)
 84{
 85	bool enabled = true;
 86	const char *opt = NULL;
 87
 88	if (video_of_only && !is_of)
 89		enabled = false;
 90
 91	opt = __video_get_option_string(name);
 92
 93	if (options)
 94		*options = opt;
 95
 96	return enabled;
 97}
 98EXPORT_SYMBOL(__video_get_options);
 99
100/*
101 * Process command line options for video adapters. This function is
102 * a __setup and __init function. It only stores the options. Drivers
103 * have to call video_get_options() as necessary.
104 */
105static int __init video_setup(char *options)
106{
107	if (!options || !*options)
108		goto out;
109
110	if (!strncmp(options, "ofonly", 6)) {
111		video_of_only = true;
112		goto out;
113	}
114
115	if (strchr(options, ':')) {
116		/* named */
117		size_t i;
118
119		for (i = 0; i < ARRAY_SIZE(video_options); i++) {
120			if (!video_options[i]) {
121				video_options[i] = options;
122				break;
123			}
124		}
125	} else {
126		/* global */
127		video_option = options;
128	}
129
130out:
131	return 1;
132}
133__setup("video=", video_setup);