arch/x86/kernel/sysfb_simplefb.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Generic System Framebuffers on x86
   4  * Copyright (c) 2012-2013 David Herrmann <dh.herrmann@gmail.com>
   5  */
   6
   7 /*
   8  * simple-framebuffer probing
   9  * Try to convert "screen_info" into a "simple-framebuffer" compatible mode.
  10  * If the mode is incompatible, we return "false" and let the caller create
  11  * legacy nodes instead.
  12  */
  13
  14 #include <linux/err.h>
  15 #include <linux/init.h>
  16 #include <linux/kernel.h>
  17 #include <linux/mm.h>
  18 #include <linux/platform_data/simplefb.h>
  19 #include <linux/platform_device.h>
  20 #include <linux/screen_info.h>
  21 #include <asm/sysfb.h>
  22
  23 static const char simplefb_resname[] = "BOOTFB";
  24 static const struct simplefb_format formats[] = SIMPLEFB_FORMATS;
  25
  26 /* try parsing x86 screen_info into a simple-framebuffer mode struct */
  27 __init bool parse_mode(const struct screen_info *si,
  28                        struct simplefb_platform_data *mode)
  29 {
  30         const struct simplefb_format *f;
  31         __u8 type;
  32         unsigned int i;
  33
  34         type = si->orig_video_isVGA;
  35         if (type != VIDEO_TYPE_VLFB && type != VIDEO_TYPE_EFI)
  36                 return false;
  37
  38         for (i = 0; i < ARRAY_SIZE(formats); ++i) {
  39                 f = &formats[i];
  40                 if (si->lfb_depth == f->bits_per_pixel &&
  41                     si->red_size == f->red.length &&
  42                     si->red_pos == f->red.offset &&
  43                     si->green_size == f->green.length &&
  44                     si->green_pos == f->green.offset &&
  45                     si->blue_size == f->blue.length &&
  46                     si->blue_pos == f->blue.offset &&
  47                     si->rsvd_size == f->transp.length &&
  48                     si->rsvd_pos == f->transp.offset) {
  49                         mode->format = f->name;
  50                         mode->width = si->lfb_width;
  51                         mode->height = si->lfb_height;
  52                         mode->stride = si->lfb_linelength;
  53                         return true;
  54                 }
  55         }
  56
  57         return false;
  58 }
  59
  60 __init int create_simplefb(const struct screen_info *si,
  61                            const struct simplefb_platform_data *mode)
  62 {
  63         struct platform_device *pd;
  64         struct resource res;
  65         u64 base, size;
  66         u32 length;
  67
  68         /*
  69          * If the 64BIT_BASE capability is set, ext_lfb_base will contain the
  70          * upper half of the base address. Assemble the address, then make sure
  71          * it is valid and we can actually access it.
  72          */
  73         base = si->lfb_base;
  74         if (si->capabilities & VIDEO_CAPABILITY_64BIT_BASE)
  75                 base |= (u64)si->ext_lfb_base << 32;
  76         if (!base || (u64)(resource_size_t)base != base) {
  77                 printk(KERN_DEBUG "sysfb: inaccessible VRAM base\n");
  78                 return -EINVAL;
  79         }
  80
  81         /*
  82          * Don't use lfb_size as IORESOURCE size, since it may contain the
  83          * entire VMEM, and thus require huge mappings. Use just the part we
  84          * need, that is, the part where the framebuffer is located. But verify
  85          * that it does not exceed the advertised VMEM.
  86          * Note that in case of VBE, the lfb_size is shifted by 16 bits for
  87          * historical reasons.
  88          */
  89         size = si->lfb_size;
  90         if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
  91                 size <<= 16;
  92         length = mode->height * mode->stride;
  93         if (length > size) {
  94                 printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
  95                 return -EINVAL;
  96         }
  97         length = PAGE_ALIGN(length);
  98
  99         /* setup IORESOURCE_MEM as framebuffer memory */
 100         memset(&res, 0, sizeof(res));
 101         res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 102         res.name = simplefb_resname;
 103         res.start = base;
 104         res.end = res.start + length - 1;
 105         if (res.end <= res.start)
 106                 return -EINVAL;
 107
 108         pd = platform_device_register_resndata(NULL, "simple-framebuffer", 0,
 109                                                &res, 1, mode, sizeof(*mode));
 110         return PTR_ERR_OR_ZERO(pd);
 111 }