drivers/firmware/sysfb_simplefb.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 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 <linux/sysfb.h>
  22
  23 static const char simplefb_resname[] = "BOOTFB";
  24 static const struct simplefb_format formats[] = SIMPLEFB_FORMATS;
  25
  26 /* try parsing screen_info into a simple-framebuffer mode struct */
  27 __init bool sysfb_parse_mode(const struct screen_info *si,
  28                              struct simplefb_platform_data *mode)
  29 {
  30         __u8 type;
  31         u32 bits_per_pixel;
  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         /*
  39          * The meaning of depth and bpp for direct-color formats is
  40          * inconsistent:
  41          *
  42          *  - DRM format info specifies depth as the number of color
  43          *    bits; including alpha, but not including filler bits.
  44          *  - Linux' EFI platform code computes lfb_depth from the
  45          *    individual color channels, including the reserved bits.
  46          *  - VBE 1.1 defines lfb_depth for XRGB1555 as 16, but later
  47          *    versions use 15.
  48          *  - On the kernel command line, 'bpp' of 32 is usually
  49          *    XRGB8888 including the filler bits, but 15 is XRGB1555
  50          *    not including the filler bit.
  51          *
  52          * It's not easily possible to fix this in struct screen_info,
  53          * as this could break UAPI. The best solution is to compute
  54          * bits_per_pixel from the color bits, reserved bits and
  55          * reported lfb_depth, whichever is highest.  In the loop below,
  56          * ignore simplefb formats with alpha bits, as EFI and VESA
  57          * don't specify alpha channels.
  58          */
  59         if (si->lfb_depth > 8) {
  60                 bits_per_pixel = max(max3(si->red_size + si->red_pos,
  61                                           si->green_size + si->green_pos,
  62                                           si->blue_size + si->blue_pos),
  63                                      si->rsvd_size + si->rsvd_pos);
  64                 bits_per_pixel = max_t(u32, bits_per_pixel, si->lfb_depth);
  65         } else {
  66                 bits_per_pixel = si->lfb_depth;
  67         }
  68
  69         for (i = 0; i < ARRAY_SIZE(formats); ++i) {
  70                 const struct simplefb_format *f = &formats[i];
  71
  72                 if (f->transp.length)
  73                         continue; /* transparent formats are unsupported by VESA/EFI */
  74
  75                 if (bits_per_pixel == f->bits_per_pixel &&
  76                     si->red_size == f->red.length &&
  77                     si->red_pos == f->red.offset &&
  78                     si->green_size == f->green.length &&
  79                     si->green_pos == f->green.offset &&
  80                     si->blue_size == f->blue.length &&
  81                     si->blue_pos == f->blue.offset) {
  82                         mode->format = f->name;
  83                         mode->width = si->lfb_width;
  84                         mode->height = si->lfb_height;
  85                         mode->stride = si->lfb_linelength;
  86                         return true;
  87                 }
  88         }
  89
  90         return false;
  91 }
  92
  93 __init struct platform_device *sysfb_create_simplefb(const struct screen_info *si,
  94                                                      const struct simplefb_platform_data *mode,
  95                                                      struct device *parent)
  96 {
  97         struct platform_device *pd;
  98         struct resource res;
  99         u64 base, size;
 100         u32 length;
 101         int ret;
 102
 103         /*
 104          * If the 64BIT_BASE capability is set, ext_lfb_base will contain the
 105          * upper half of the base address. Assemble the address, then make sure
 106          * it is valid and we can actually access it.
 107          */
 108         base = si->lfb_base;
 109         if (si->capabilities & VIDEO_CAPABILITY_64BIT_BASE)
 110                 base |= (u64)si->ext_lfb_base << 32;
 111         if (!base || (u64)(resource_size_t)base != base) {
 112                 printk(KERN_DEBUG "sysfb: inaccessible VRAM base\n");
 113                 return ERR_PTR(-EINVAL);
 114         }
 115
 116         /*
 117          * Don't use lfb_size as IORESOURCE size, since it may contain the
 118          * entire VMEM, and thus require huge mappings. Use just the part we
 119          * need, that is, the part where the framebuffer is located. But verify
 120          * that it does not exceed the advertised VMEM.
 121          * Note that in case of VBE, the lfb_size is shifted by 16 bits for
 122          * historical reasons.
 123          */
 124         size = si->lfb_size;
 125         if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
 126                 size <<= 16;
 127         length = mode->height * mode->stride;
 128         if (length > size) {
 129                 printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
 130                 return ERR_PTR(-EINVAL);
 131         }
 132         length = PAGE_ALIGN(length);
 133
 134         /* setup IORESOURCE_MEM as framebuffer memory */
 135         memset(&res, 0, sizeof(res));
 136         res.flags = IORESOURCE_MEM;
 137         res.name = simplefb_resname;
 138         res.start = base;
 139         res.end = res.start + length - 1;
 140         if (res.end <= res.start)
 141                 return ERR_PTR(-EINVAL);
 142
 143         pd = platform_device_alloc("simple-framebuffer", 0);
 144         if (!pd)
 145                 return ERR_PTR(-ENOMEM);
 146
 147         pd->dev.parent = parent;
 148
 149         sysfb_set_efifb_fwnode(pd);
 150
 151         ret = platform_device_add_resources(pd, &res, 1);
 152         if (ret)
 153                 goto err_put_device;
 154
 155         ret = platform_device_add_data(pd, mode, sizeof(*mode));
 156         if (ret)
 157                 goto err_put_device;
 158
 159         ret = platform_device_add(pd);
 160         if (ret)
 161                 goto err_put_device;
 162
 163         return pd;
 164
 165 err_put_device:
 166         platform_device_put(pd);
 167
 168         return ERR_PTR(ret);
 169 }