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 here and ignore lfb_depth. In the loop below,
55 	 * ignore simplefb formats with alpha bits, as EFI and VESA
56 	 * don't specify alpha channels.
57 	 */
58 	if (si->lfb_depth > 8) {
59 		bits_per_pixel = max(max3(si->red_size + si->red_pos,
60 					  si->green_size + si->green_pos,
61 					  si->blue_size + si->blue_pos),
62 				     si->rsvd_size + si->rsvd_pos);
63 	} else {
64 		bits_per_pixel = si->lfb_depth;
65 	}
66 
67 	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
68 		const struct simplefb_format *f = &formats[i];
69 
70 		if (f->transp.length)
71 			continue; /* transparent formats are unsupported by VESA/EFI */
72 
73 		if (bits_per_pixel == f->bits_per_pixel &&
74 		    si->red_size == f->red.length &&
75 		    si->red_pos == f->red.offset &&
76 		    si->green_size == f->green.length &&
77 		    si->green_pos == f->green.offset &&
78 		    si->blue_size == f->blue.length &&
79 		    si->blue_pos == f->blue.offset) {
80 			mode->format = f->name;
81 			mode->width = si->lfb_width;
82 			mode->height = si->lfb_height;
83 			mode->stride = si->lfb_linelength;
84 			return true;
85 		}
86 	}
87 
88 	return false;
89 }
90 
91 __init struct platform_device *sysfb_create_simplefb(const struct screen_info *si,
92 						     const struct simplefb_platform_data *mode)
93 {
94 	struct platform_device *pd;
95 	struct resource res;
96 	u64 base, size;
97 	u32 length;
98 	int ret;
99 
100 	/*
101 	 * If the 64BIT_BASE capability is set, ext_lfb_base will contain the
102 	 * upper half of the base address. Assemble the address, then make sure
103 	 * it is valid and we can actually access it.
104 	 */
105 	base = si->lfb_base;
106 	if (si->capabilities & VIDEO_CAPABILITY_64BIT_BASE)
107 		base |= (u64)si->ext_lfb_base << 32;
108 	if (!base || (u64)(resource_size_t)base != base) {
109 		printk(KERN_DEBUG "sysfb: inaccessible VRAM base\n");
110 		return ERR_PTR(-EINVAL);
111 	}
112 
113 	/*
114 	 * Don't use lfb_size as IORESOURCE size, since it may contain the
115 	 * entire VMEM, and thus require huge mappings. Use just the part we
116 	 * need, that is, the part where the framebuffer is located. But verify
117 	 * that it does not exceed the advertised VMEM.
118 	 * Note that in case of VBE, the lfb_size is shifted by 16 bits for
119 	 * historical reasons.
120 	 */
121 	size = si->lfb_size;
122 	if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
123 		size <<= 16;
124 	length = mode->height * mode->stride;
125 	if (length > size) {
126 		printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
127 		return ERR_PTR(-EINVAL);
128 	}
129 	length = PAGE_ALIGN(length);
130 
131 	/* setup IORESOURCE_MEM as framebuffer memory */
132 	memset(&res, 0, sizeof(res));
133 	res.flags = IORESOURCE_MEM;
134 	res.name = simplefb_resname;
135 	res.start = base;
136 	res.end = res.start + length - 1;
137 	if (res.end <= res.start)
138 		return ERR_PTR(-EINVAL);
139 
140 	pd = platform_device_alloc("simple-framebuffer", 0);
141 	if (!pd)
142 		return ERR_PTR(-ENOMEM);
143 
144 	sysfb_apply_efi_quirks(pd);
145 
146 	ret = platform_device_add_resources(pd, &res, 1);
147 	if (ret)
148 		goto err_put_device;
149 
150 	ret = platform_device_add_data(pd, mode, sizeof(*mode));
151 	if (ret)
152 		goto err_put_device;
153 
154 	ret = platform_device_add(pd);
155 	if (ret)
156 		goto err_put_device;
157 
158 	return pd;
159 
160 err_put_device:
161 	platform_device_put(pd);
162 
163 	return ERR_PTR(ret);
164 }
165