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/pci.h>
33 #include <linux/platform_data/simplefb.h>
34 #include <linux/platform_device.h>
35 #include <linux/screen_info.h>
36 #include <linux/sysfb.h>
37
38 static struct platform_device *pd;
39 static DEFINE_MUTEX(disable_lock);
40 static bool disabled;
41
42 static struct device *sysfb_parent_dev(const struct screen_info *si);
43
sysfb_unregister(void)44 static bool sysfb_unregister(void)
45 {
46 if (IS_ERR_OR_NULL(pd))
47 return false;
48
49 platform_device_unregister(pd);
50 pd = NULL;
51
52 return true;
53 }
54
55 /**
56 * sysfb_disable() - disable the Generic System Framebuffers support
57 * @dev: the device to check if non-NULL
58 *
59 * This disables the registration of system framebuffer devices that match the
60 * generic drivers that make use of the system framebuffer set up by firmware.
61 *
62 * It also unregisters a device if this was already registered by sysfb_init().
63 *
64 * Context: The function can sleep. A @disable_lock mutex is acquired to serialize
65 * against sysfb_init(), that registers a system framebuffer device.
66 */
sysfb_disable(struct device * dev)67 void sysfb_disable(struct device *dev)
68 {
69 struct screen_info *si = &screen_info;
70 struct device *parent;
71
72 mutex_lock(&disable_lock);
73 parent = sysfb_parent_dev(si);
74 if (!dev || !parent || dev == parent) {
75 sysfb_unregister();
76 disabled = true;
77 }
78 mutex_unlock(&disable_lock);
79 }
80 EXPORT_SYMBOL_GPL(sysfb_disable);
81
82 #if defined(CONFIG_PCI)
sysfb_pci_dev_is_enabled(struct pci_dev * pdev)83 static bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev)
84 {
85 /*
86 * TODO: Try to integrate this code into the PCI subsystem
87 */
88 int ret;
89 u16 command;
90
91 ret = pci_read_config_word(pdev, PCI_COMMAND, &command);
92 if (ret != PCIBIOS_SUCCESSFUL)
93 return false;
94 if (!(command & PCI_COMMAND_MEMORY))
95 return false;
96 return true;
97 }
98 #else
sysfb_pci_dev_is_enabled(struct pci_dev * pdev)99 static bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev)
100 {
101 return false;
102 }
103 #endif
104
sysfb_parent_dev(const struct screen_info * si)105 static struct device *sysfb_parent_dev(const struct screen_info *si)
106 {
107 struct pci_dev *pdev;
108
109 pdev = screen_info_pci_dev(si);
110 if (IS_ERR(pdev)) {
111 return ERR_CAST(pdev);
112 } else if (pdev) {
113 if (!sysfb_pci_dev_is_enabled(pdev)) {
114 pci_dev_put(pdev);
115 return ERR_PTR(-ENODEV);
116 }
117 return &pdev->dev;
118 }
119
120 return NULL;
121 }
122
sysfb_init(void)123 static __init int sysfb_init(void)
124 {
125 struct screen_info *si = &screen_info;
126 struct device *parent;
127 unsigned int type;
128 struct simplefb_platform_data mode;
129 const char *name;
130 bool compatible;
131 int ret = 0;
132
133 screen_info_apply_fixups();
134
135 mutex_lock(&disable_lock);
136 if (disabled)
137 goto unlock_mutex;
138
139 sysfb_apply_efi_quirks();
140
141 parent = sysfb_parent_dev(si);
142 if (IS_ERR(parent)) {
143 ret = PTR_ERR(parent);
144 goto unlock_mutex;
145 }
146
147 /* try to create a simple-framebuffer device */
148 compatible = sysfb_parse_mode(si, &mode);
149 if (compatible) {
150 pd = sysfb_create_simplefb(si, &mode, parent);
151 if (!IS_ERR(pd))
152 goto put_device;
153 }
154
155 type = screen_info_video_type(si);
156
157 /* if the FB is incompatible, create a legacy framebuffer device */
158 switch (type) {
159 case VIDEO_TYPE_EGAC:
160 name = "ega-framebuffer";
161 break;
162 case VIDEO_TYPE_VGAC:
163 name = "vga-framebuffer";
164 break;
165 case VIDEO_TYPE_VLFB:
166 name = "vesa-framebuffer";
167 break;
168 case VIDEO_TYPE_EFI:
169 name = "efi-framebuffer";
170 break;
171 default:
172 name = "platform-framebuffer";
173 break;
174 }
175
176 pd = platform_device_alloc(name, 0);
177 if (!pd) {
178 ret = -ENOMEM;
179 goto put_device;
180 }
181
182 pd->dev.parent = parent;
183
184 sysfb_set_efifb_fwnode(pd);
185
186 ret = platform_device_add_data(pd, si, sizeof(*si));
187 if (ret)
188 goto err;
189
190 ret = platform_device_add(pd);
191 if (ret)
192 goto err;
193
194 goto put_device;
195 err:
196 platform_device_put(pd);
197 put_device:
198 put_device(parent);
199 unlock_mutex:
200 mutex_unlock(&disable_lock);
201 return ret;
202 }
203
204 /* must execute after PCI subsystem for EFI quirks */
205 device_initcall(sysfb_init);
206