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 	mutex_lock(&disable_lock);
81 	if (disabled)
82 		goto unlock_mutex;
83 
84 	/* try to create a simple-framebuffer device */
85 	compatible = sysfb_parse_mode(si, &mode);
86 	if (compatible) {
87 		pd = sysfb_create_simplefb(si, &mode);
88 		if (!IS_ERR(pd))
89 			goto unlock_mutex;
90 	}
91 
92 	/* if the FB is incompatible, create a legacy framebuffer device */
93 	if (si->orig_video_isVGA == VIDEO_TYPE_EFI)
94 		name = "efi-framebuffer";
95 	else if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
96 		name = "vesa-framebuffer";
97 	else if (si->orig_video_isVGA == VIDEO_TYPE_VGAC)
98 		name = "vga-framebuffer";
99 	else if (si->orig_video_isVGA == VIDEO_TYPE_EGAC)
100 		name = "ega-framebuffer";
101 	else
102 		name = "platform-framebuffer";
103 
104 	pd = platform_device_alloc(name, 0);
105 	if (!pd) {
106 		ret = -ENOMEM;
107 		goto unlock_mutex;
108 	}
109 
110 	sysfb_apply_efi_quirks(pd);
111 
112 	ret = platform_device_add_data(pd, si, sizeof(*si));
113 	if (ret)
114 		goto err;
115 
116 	ret = platform_device_add(pd);
117 	if (ret)
118 		goto err;
119 
120 	goto unlock_mutex;
121 err:
122 	platform_device_put(pd);
123 unlock_mutex:
124 	mutex_unlock(&disable_lock);
125 	return ret;
126 }
127 
128 /* must execute after PCI subsystem for EFI quirks */
129 device_initcall(sysfb_init);
130