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 */
sysfb_parse_mode(const struct screen_info * si,struct simplefb_platform_data * mode)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
sysfb_create_simplefb(const struct screen_info * si,const struct simplefb_platform_data * mode)93 __init struct platform_device *sysfb_create_simplefb(const struct screen_info *si,
94 const struct simplefb_platform_data *mode)
95 {
96 struct platform_device *pd;
97 struct resource res;
98 u64 base, size;
99 u32 length;
100 int ret;
101
102 /*
103 * If the 64BIT_BASE capability is set, ext_lfb_base will contain the
104 * upper half of the base address. Assemble the address, then make sure
105 * it is valid and we can actually access it.
106 */
107 base = si->lfb_base;
108 if (si->capabilities & VIDEO_CAPABILITY_64BIT_BASE)
109 base |= (u64)si->ext_lfb_base << 32;
110 if (!base || (u64)(resource_size_t)base != base) {
111 printk(KERN_DEBUG "sysfb: inaccessible VRAM base\n");
112 return ERR_PTR(-EINVAL);
113 }
114
115 /*
116 * Don't use lfb_size as IORESOURCE size, since it may contain the
117 * entire VMEM, and thus require huge mappings. Use just the part we
118 * need, that is, the part where the framebuffer is located. But verify
119 * that it does not exceed the advertised VMEM.
120 * Note that in case of VBE, the lfb_size is shifted by 16 bits for
121 * historical reasons.
122 */
123 size = si->lfb_size;
124 if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
125 size <<= 16;
126 length = mode->height * mode->stride;
127 if (length > size) {
128 printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
129 return ERR_PTR(-EINVAL);
130 }
131 length = PAGE_ALIGN(length);
132
133 /* setup IORESOURCE_MEM as framebuffer memory */
134 memset(&res, 0, sizeof(res));
135 res.flags = IORESOURCE_MEM;
136 res.name = simplefb_resname;
137 res.start = base;
138 res.end = res.start + length - 1;
139 if (res.end <= res.start)
140 return ERR_PTR(-EINVAL);
141
142 pd = platform_device_alloc("simple-framebuffer", 0);
143 if (!pd)
144 return ERR_PTR(-ENOMEM);
145
146 sysfb_set_efifb_fwnode(pd);
147
148 ret = platform_device_add_resources(pd, &res, 1);
149 if (ret)
150 goto err_put_device;
151
152 ret = platform_device_add_data(pd, mode, sizeof(*mode));
153 if (ret)
154 goto err_put_device;
155
156 ret = platform_device_add(pd);
157 if (ret)
158 goto err_put_device;
159
160 return pd;
161
162 err_put_device:
163 platform_device_put(pd);
164
165 return ERR_PTR(ret);
166 }
167