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 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  */
  64 void sysfb_disable(void)
  65 {
  66         mutex_lock(&disable_lock);
  67         sysfb_unregister();
  68         disabled = true;
  69         mutex_unlock(&disable_lock);
  70 }
  71 EXPORT_SYMBOL_GPL(sysfb_disable);
  72
  73 #if defined(CONFIG_PCI)
  74 static __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
  90 static __init bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev)
  91 {
  92         return false;
  93 }
  94 #endif
  95
  96 static __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                         pci_dev_put(pdev);
 106                         return ERR_PTR(-ENODEV);
 107                 }
 108                 return &pdev->dev;
 109         }
 110
 111         return NULL;
 112 }
 113
 114 static __init int sysfb_init(void)
 115 {
 116         struct screen_info *si = &screen_info;
 117         struct device *parent;
 118         struct simplefb_platform_data mode;
 119         const char *name;
 120         bool compatible;
 121         int ret = 0;
 122
 123         screen_info_apply_fixups();
 124
 125         mutex_lock(&disable_lock);
 126         if (disabled)
 127                 goto unlock_mutex;
 128
 129         sysfb_apply_efi_quirks();
 130
 131         parent = sysfb_parent_dev(si);
 132         if (IS_ERR(parent)) {
 133                 ret = PTR_ERR(parent);
 134                 goto unlock_mutex;
 135         }
 136
 137         /* try to create a simple-framebuffer device */
 138         compatible = sysfb_parse_mode(si, &mode);
 139         if (compatible) {
 140                 pd = sysfb_create_simplefb(si, &mode, parent);
 141                 if (!IS_ERR(pd))
 142                         goto put_device;
 143         }
 144
 145         /* if the FB is incompatible, create a legacy framebuffer device */
 146         if (si->orig_video_isVGA == VIDEO_TYPE_EFI)
 147                 name = "efi-framebuffer";
 148         else if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
 149                 name = "vesa-framebuffer";
 150         else if (si->orig_video_isVGA == VIDEO_TYPE_VGAC)
 151                 name = "vga-framebuffer";
 152         else if (si->orig_video_isVGA == VIDEO_TYPE_EGAC)
 153                 name = "ega-framebuffer";
 154         else
 155                 name = "platform-framebuffer";
 156
 157         pd = platform_device_alloc(name, 0);
 158         if (!pd) {
 159                 ret = -ENOMEM;
 160                 goto put_device;
 161         }
 162
 163         pd->dev.parent = parent;
 164
 165         sysfb_set_efifb_fwnode(pd);
 166
 167         ret = platform_device_add_data(pd, si, sizeof(*si));
 168         if (ret)
 169                 goto err;
 170
 171         ret = platform_device_add(pd);
 172         if (ret)
 173                 goto err;
 174
 175         goto put_device;
 176 err:
 177         platform_device_put(pd);
 178 put_device:
 179         put_device(parent);
 180 unlock_mutex:
 181         mutex_unlock(&disable_lock);
 182         return ret;
 183 }
 184
 185 /* must execute after PCI subsystem for EFI quirks */
 186 device_initcall(sysfb_init);