1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * cbmem.c
4 *
5 * Driver for exporting cbmem entries in sysfs.
6 *
7 * Copyright 2022 Google LLC
8 */
9
10 #include <linux/device.h>
11 #include <linux/init.h>
12 #include <linux/io.h>
13 #include <linux/kernel.h>
14 #include <linux/kobject.h>
15 #include <linux/module.h>
16 #include <linux/platform_device.h>
17 #include <linux/slab.h>
18 #include <linux/sysfs.h>
19
20 #include "coreboot_table.h"
21
22 struct cbmem_entry {
23 char *mem_file_buf;
24 u32 size;
25 };
26
to_cbmem_entry(struct kobject * kobj)27 static struct cbmem_entry *to_cbmem_entry(struct kobject *kobj)
28 {
29 return dev_get_drvdata(kobj_to_dev(kobj));
30 }
31
mem_read(struct file * filp,struct kobject * kobj,struct bin_attribute * bin_attr,char * buf,loff_t pos,size_t count)32 static ssize_t mem_read(struct file *filp, struct kobject *kobj,
33 struct bin_attribute *bin_attr, char *buf, loff_t pos,
34 size_t count)
35 {
36 struct cbmem_entry *entry = to_cbmem_entry(kobj);
37
38 return memory_read_from_buffer(buf, count, &pos, entry->mem_file_buf,
39 entry->size);
40 }
41
mem_write(struct file * filp,struct kobject * kobj,struct bin_attribute * bin_attr,char * buf,loff_t pos,size_t count)42 static ssize_t mem_write(struct file *filp, struct kobject *kobj,
43 struct bin_attribute *bin_attr, char *buf, loff_t pos,
44 size_t count)
45 {
46 struct cbmem_entry *entry = to_cbmem_entry(kobj);
47
48 if (pos < 0 || pos >= entry->size)
49 return -EINVAL;
50 if (count > entry->size - pos)
51 count = entry->size - pos;
52
53 memcpy(entry->mem_file_buf + pos, buf, count);
54 return count;
55 }
56 static BIN_ATTR_ADMIN_RW(mem, 0);
57
address_show(struct device * dev,struct device_attribute * attr,char * buf)58 static ssize_t address_show(struct device *dev, struct device_attribute *attr,
59 char *buf)
60 {
61 struct coreboot_device *cbdev = dev_to_coreboot_device(dev);
62
63 return sysfs_emit(buf, "0x%llx\n", cbdev->cbmem_entry.address);
64 }
65 static DEVICE_ATTR_RO(address);
66
size_show(struct device * dev,struct device_attribute * attr,char * buf)67 static ssize_t size_show(struct device *dev, struct device_attribute *attr,
68 char *buf)
69 {
70 struct coreboot_device *cbdev = dev_to_coreboot_device(dev);
71
72 return sysfs_emit(buf, "0x%x\n", cbdev->cbmem_entry.entry_size);
73 }
74 static DEVICE_ATTR_RO(size);
75
76 static struct attribute *attrs[] = {
77 &dev_attr_address.attr,
78 &dev_attr_size.attr,
79 NULL,
80 };
81
82 static struct bin_attribute *bin_attrs[] = {
83 &bin_attr_mem,
84 NULL,
85 };
86
87 static const struct attribute_group cbmem_entry_group = {
88 .attrs = attrs,
89 .bin_attrs = bin_attrs,
90 };
91
92 static const struct attribute_group *dev_groups[] = {
93 &cbmem_entry_group,
94 NULL,
95 };
96
cbmem_entry_probe(struct coreboot_device * dev)97 static int cbmem_entry_probe(struct coreboot_device *dev)
98 {
99 struct cbmem_entry *entry;
100
101 entry = devm_kzalloc(&dev->dev, sizeof(*entry), GFP_KERNEL);
102 if (!entry)
103 return -ENOMEM;
104
105 dev_set_drvdata(&dev->dev, entry);
106 entry->mem_file_buf = devm_memremap(&dev->dev, dev->cbmem_entry.address,
107 dev->cbmem_entry.entry_size,
108 MEMREMAP_WB);
109 if (IS_ERR(entry->mem_file_buf))
110 return PTR_ERR(entry->mem_file_buf);
111
112 entry->size = dev->cbmem_entry.entry_size;
113
114 return 0;
115 }
116
117 static const struct coreboot_device_id cbmem_ids[] = {
118 { .tag = LB_TAG_CBMEM_ENTRY },
119 { /* sentinel */ }
120 };
121 MODULE_DEVICE_TABLE(coreboot, cbmem_ids);
122
123 static struct coreboot_driver cbmem_entry_driver = {
124 .probe = cbmem_entry_probe,
125 .drv = {
126 .name = "cbmem",
127 .dev_groups = dev_groups,
128 },
129 .id_table = cbmem_ids,
130 };
131 module_coreboot_driver(cbmem_entry_driver);
132
133 MODULE_AUTHOR("Jack Rosenthal <jrosenth@chromium.org>");
134 MODULE_DESCRIPTION("Driver for exporting CBMEM entries in sysfs");
135 MODULE_LICENSE("GPL");
136