1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include <linux/pci.h>
4 #include <linux/printk.h>
5 #include <linux/screen_info.h>
6 #include <linux/string.h>
7 
8 static struct pci_dev *screen_info_lfb_pdev;
9 static size_t screen_info_lfb_bar;
10 static resource_size_t screen_info_lfb_offset;
11 static struct resource screen_info_lfb_res = DEFINE_RES_MEM(0, 0);
12 
13 static bool __screen_info_relocation_is_valid(const struct screen_info *si, struct resource *pr)
14 {
15 	u64 size = __screen_info_lfb_size(si, screen_info_video_type(si));
16 
17 	if (screen_info_lfb_offset > resource_size(pr))
18 		return false;
19 	if (size > resource_size(pr))
20 		return false;
21 	if (resource_size(pr) - size < screen_info_lfb_offset)
22 		return false;
23 
24 	return true;
25 }
26 
27 void screen_info_apply_fixups(void)
28 {
29 	struct screen_info *si = &screen_info;
30 
31 	if (screen_info_lfb_pdev) {
32 		struct resource *pr = &screen_info_lfb_pdev->resource[screen_info_lfb_bar];
33 
34 		if (pr->start != screen_info_lfb_res.start) {
35 			if (__screen_info_relocation_is_valid(si, pr)) {
36 				/*
37 				 * Only update base if we have an actual
38 				 * relocation to a valid I/O range.
39 				 */
40 				__screen_info_set_lfb_base(si, pr->start + screen_info_lfb_offset);
41 				pr_info("Relocating firmware framebuffer to offset %pa[d] within %pr\n",
42 					&screen_info_lfb_offset, pr);
43 			} else {
44 				pr_warn("Invalid relocating, disabling firmware framebuffer\n");
45 			}
46 		}
47 	}
48 }
49 
50 static void screen_info_fixup_lfb(struct pci_dev *pdev)
51 {
52 	unsigned int type;
53 	struct resource res[SCREEN_INFO_MAX_RESOURCES];
54 	size_t i, numres;
55 	int ret;
56 	const struct screen_info *si = &screen_info;
57 
58 	if (screen_info_lfb_pdev)
59 		return; // already found
60 
61 	type = screen_info_video_type(si);
62 	if (type != VIDEO_TYPE_EFI)
63 		return; // only applies to EFI
64 
65 	ret = screen_info_resources(si, res, ARRAY_SIZE(res));
66 	if (ret < 0)
67 		return;
68 	numres = ret;
69 
70 	for (i = 0; i < numres; ++i) {
71 		struct resource *r = &res[i];
72 		const struct resource *pr;
73 
74 		if (!(r->flags & IORESOURCE_MEM))
75 			continue;
76 		pr = pci_find_resource(pdev, r);
77 		if (!pr)
78 			continue;
79 
80 		/*
81 		 * We've found a PCI device with the framebuffer
82 		 * resource. Store away the parameters to track
83 		 * relocation of the framebuffer aperture.
84 		 */
85 		screen_info_lfb_pdev = pdev;
86 		screen_info_lfb_bar = pr - pdev->resource;
87 		screen_info_lfb_offset = r->start - pr->start;
88 		memcpy(&screen_info_lfb_res, r, sizeof(screen_info_lfb_res));
89 	}
90 }
91 DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY, 16,
92 			       screen_info_fixup_lfb);
93 
94 static struct pci_dev *__screen_info_pci_dev(struct resource *res)
95 {
96 	struct pci_dev *pdev = NULL;
97 	const struct resource *r = NULL;
98 
99 	if (!(res->flags & IORESOURCE_MEM))
100 		return NULL;
101 
102 	while (!r && (pdev = pci_get_base_class(PCI_BASE_CLASS_DISPLAY, pdev))) {
103 		r = pci_find_resource(pdev, res);
104 	}
105 
106 	return pdev;
107 }
108 
109 /**
110  * screen_info_pci_dev() - Return PCI parent device that contains screen_info's framebuffer
111  * @si: the screen_info
112  *
113  * Returns:
114  * The screen_info's parent device or NULL on success, or a pointer-encoded
115  * errno value otherwise. The value NULL is not an error. It signals that no
116  * PCI device has been found.
117  */
118 struct pci_dev *screen_info_pci_dev(const struct screen_info *si)
119 {
120 	struct resource res[SCREEN_INFO_MAX_RESOURCES];
121 	ssize_t i, numres;
122 
123 	numres = screen_info_resources(si, res, ARRAY_SIZE(res));
124 	if (numres < 0)
125 		return ERR_PTR(numres);
126 
127 	for (i = 0; i < numres; ++i) {
128 		struct pci_dev *pdev = __screen_info_pci_dev(&res[i]);
129 
130 		if (pdev)
131 			return pdev;
132 	}
133 
134 	return NULL;
135 }
136 EXPORT_SYMBOL(screen_info_pci_dev);
137