drivers/firmware/sysfb.c

   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
  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  */
  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 /**
  83  * sysfb_handles_screen_info() - reports if sysfb handles the global screen_info
  84  *
  85  * Callers can use sysfb_handles_screen_info() to determine whether the Generic
  86  * System Framebuffers (sysfb) can handle the global screen_info data structure
  87  * or not. Drivers might need this information to know if they have to setup the
  88  * system framebuffer, or if they have to delegate this action to sysfb instead.
  89  *
  90  * Returns:
  91  * True if sysfb handles the global screen_info data structure.
  92  */
  93 bool sysfb_handles_screen_info(void)
  94 {
  95         const struct screen_info *si = &screen_info;
  96
  97         return !!screen_info_video_type(si);
  98 }
  99 EXPORT_SYMBOL_GPL(sysfb_handles_screen_info);
 100
 101 #if defined(CONFIG_PCI)
 102 static bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev)
 103 {
 104         /*
 105          * TODO: Try to integrate this code into the PCI subsystem
 106          */
 107         int ret;
 108         u16 command;
 109
 110         ret = pci_read_config_word(pdev, PCI_COMMAND, &command);
 111         if (ret != PCIBIOS_SUCCESSFUL)
 112                 return false;
 113         if (!(command & PCI_COMMAND_MEMORY))
 114                 return false;
 115         return true;
 116 }
 117 #else
 118 static bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev)
 119 {
 120         return false;
 121 }
 122 #endif
 123
 124 static struct device *sysfb_parent_dev(const struct screen_info *si)
 125 {
 126         struct pci_dev *pdev;
 127
 128         pdev = screen_info_pci_dev(si);
 129         if (IS_ERR(pdev)) {
 130                 return ERR_CAST(pdev);
 131         } else if (pdev) {
 132                 if (!sysfb_pci_dev_is_enabled(pdev)) {
 133                         pci_dev_put(pdev);
 134                         return ERR_PTR(-ENODEV);
 135                 }
 136                 return &pdev->dev;
 137         }
 138
 139         return NULL;
 140 }
 141
 142 static __init int sysfb_init(void)
 143 {
 144         struct screen_info *si = &screen_info;
 145         struct device *parent;
 146         struct simplefb_platform_data mode;
 147         const char *name;
 148         bool compatible;
 149         int ret = 0;
 150
 151         screen_info_apply_fixups();
 152
 153         mutex_lock(&disable_lock);
 154         if (disabled)
 155                 goto unlock_mutex;
 156
 157         sysfb_apply_efi_quirks();
 158
 159         parent = sysfb_parent_dev(si);
 160         if (IS_ERR(parent)) {
 161                 ret = PTR_ERR(parent);
 162                 goto unlock_mutex;
 163         }
 164
 165         /* try to create a simple-framebuffer device */
 166         compatible = sysfb_parse_mode(si, &mode);
 167         if (compatible) {
 168                 pd = sysfb_create_simplefb(si, &mode, parent);
 169                 if (!IS_ERR(pd))
 170                         goto put_device;
 171         }
 172
 173         /* if the FB is incompatible, create a legacy framebuffer device */
 174         if (si->orig_video_isVGA == VIDEO_TYPE_EFI)
 175                 name = "efi-framebuffer";
 176         else if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
 177                 name = "vesa-framebuffer";
 178         else if (si->orig_video_isVGA == VIDEO_TYPE_VGAC)
 179                 name = "vga-framebuffer";
 180         else if (si->orig_video_isVGA == VIDEO_TYPE_EGAC)
 181                 name = "ega-framebuffer";
 182         else
 183                 name = "platform-framebuffer";
 184
 185         pd = platform_device_alloc(name, 0);
 186         if (!pd) {
 187                 ret = -ENOMEM;
 188                 goto put_device;
 189         }
 190
 191         pd->dev.parent = parent;
 192
 193         sysfb_set_efifb_fwnode(pd);
 194
 195         ret = platform_device_add_data(pd, si, sizeof(*si));
 196         if (ret)
 197                 goto err;
 198
 199         ret = platform_device_add(pd);
 200         if (ret)
 201                 goto err;
 202
 203         goto put_device;
 204 err:
 205         platform_device_put(pd);
 206 put_device:
 207         put_device(parent);
 208 unlock_mutex:
 209         mutex_unlock(&disable_lock);
 210         return ret;
 211 }
 212
 213 /* must execute after PCI subsystem for EFI quirks */
 214 device_initcall(sysfb_init);