drivers/video/cmdline.c

   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  */
  29 static const char *video_options[FB_MAX] __read_mostly;
  30 static const char *video_option __read_mostly;
  31 static int video_of_only __read_mostly;
  32
  33 static 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  */
  77 const char *video_get_options(const char *name)
  78 {
  79         return __video_get_option_string(name);
  80 }
  81 EXPORT_SYMBOL(video_get_options);
  82
  83 #if IS_ENABLED(CONFIG_FB_CORE)
  84 bool __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 }
  99 EXPORT_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  */
 107 static 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
 132 out:
 133         return 1;
 134 }
 135 __setup("video=", video_setup);