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