1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Generic System Framebuffers
4 * Copyright (c) 2012-2013 David Herrmann <dh.herrmann@gmail.com>
5 */
6
7 /*
8 * Simple-Framebuffer support
9 * Create a platform-device for any available boot framebuffer. The
10 * simple-framebuffer platform device is already available on DT systems, so
11 * this module parses the global "screen_info" object and creates a suitable
12 * platform device compatible with the "simple-framebuffer" DT object. If
13 * the framebuffer is incompatible, we instead create a legacy
14 * "vesa-framebuffer", "efi-framebuffer" or "platform-framebuffer" device and
15 * pass the screen_info as platform_data. This allows legacy drivers
16 * to pick these devices up without messing with simple-framebuffer drivers.
17 * The global "screen_info" is still valid at all times.
18 *
19 * If CONFIG_SYSFB_SIMPLEFB is not selected, never register "simple-framebuffer"
20 * platform devices, but only use legacy framebuffer devices for
21 * backwards compatibility.
22 *
23 * TODO: We set the dev_id field of all platform-devices to 0. This allows
24 * other OF/DT parsers to create such devices, too. However, they must
25 * start at offset 1 for this to work.
26 */
27
28 #include <linux/err.h>
29 #include <linux/init.h>
30 #include <linux/kernel.h>
31 #include <linux/mm.h>
32 #include <linux/platform_data/simplefb.h>
33 #include <linux/platform_device.h>
34 #include <linux/screen_info.h>
35 #include <linux/sysfb.h>
36
37 static struct platform_device *pd;
38 static DEFINE_MUTEX(disable_lock);
39 static bool disabled;
40
sysfb_unregister(void)41 static bool sysfb_unregister(void)
42 {
43 if (IS_ERR_OR_NULL(pd))
44 return false;
45
46 platform_device_unregister(pd);
47 pd = NULL;
48
49 return true;
50 }
51
52 /**
53 * sysfb_disable() - disable the Generic System Framebuffers support
54 *
55 * This disables the registration of system framebuffer devices that match the
56 * generic drivers that make use of the system framebuffer set up by firmware.
57 *
58 * It also unregisters a device if this was already registered by sysfb_init().
59 *
60 * Context: The function can sleep. A @disable_lock mutex is acquired to serialize
61 * against sysfb_init(), that registers a system framebuffer device.
62 */
sysfb_disable(void)63 void sysfb_disable(void)
64 {
65 mutex_lock(&disable_lock);
66 sysfb_unregister();
67 disabled = true;
68 mutex_unlock(&disable_lock);
69 }
70 EXPORT_SYMBOL_GPL(sysfb_disable);
71
sysfb_init(void)72 static __init int sysfb_init(void)
73 {
74 struct screen_info *si = &screen_info;
75 struct simplefb_platform_data mode;
76 const char *name;
77 bool compatible;
78 int ret = 0;
79
80 screen_info_apply_fixups();
81
82 mutex_lock(&disable_lock);
83 if (disabled)
84 goto unlock_mutex;
85
86 sysfb_apply_efi_quirks();
87
88 /* try to create a simple-framebuffer device */
89 compatible = sysfb_parse_mode(si, &mode);
90 if (compatible) {
91 pd = sysfb_create_simplefb(si, &mode);
92 if (!IS_ERR(pd))
93 goto unlock_mutex;
94 }
95
96 /* if the FB is incompatible, create a legacy framebuffer device */
97 if (si->orig_video_isVGA == VIDEO_TYPE_EFI)
98 name = "efi-framebuffer";
99 else if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
100 name = "vesa-framebuffer";
101 else if (si->orig_video_isVGA == VIDEO_TYPE_VGAC)
102 name = "vga-framebuffer";
103 else if (si->orig_video_isVGA == VIDEO_TYPE_EGAC)
104 name = "ega-framebuffer";
105 else
106 name = "platform-framebuffer";
107
108 pd = platform_device_alloc(name, 0);
109 if (!pd) {
110 ret = -ENOMEM;
111 goto unlock_mutex;
112 }
113
114 sysfb_set_efifb_fwnode(pd);
115
116 ret = platform_device_add_data(pd, si, sizeof(*si));
117 if (ret)
118 goto err;
119
120 ret = platform_device_add(pd);
121 if (ret)
122 goto err;
123
124 goto unlock_mutex;
125 err:
126 platform_device_put(pd);
127 unlock_mutex:
128 mutex_unlock(&disable_lock);
129 return ret;
130 }
131
132 /* must execute after PCI subsystem for EFI quirks */
133 device_initcall(sysfb_init);
134