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/device-id/coreboot.h>
16 #include <linux/module.h>
17 #include <linux/platform_device.h>
18 #include <linux/slab.h>
19 #include <linux/sysfs.h>
20
21 #include "coreboot_table.h"
22
23 struct cbmem_entry {
24 char *mem_file_buf;
25 u32 size;
26 };
27
to_cbmem_entry(struct kobject * kobj)28 static struct cbmem_entry *to_cbmem_entry(struct kobject *kobj)
29 {
30 return dev_get_drvdata(kobj_to_dev(kobj));
31 }
32
mem_read(struct file * filp,struct kobject * kobj,const struct bin_attribute * bin_attr,char * buf,loff_t pos,size_t count)33 static ssize_t mem_read(struct file *filp, struct kobject *kobj,
34 const struct bin_attribute *bin_attr, char *buf, loff_t pos,
35 size_t count)
36 {
37 struct cbmem_entry *entry = to_cbmem_entry(kobj);
38
39 return memory_read_from_buffer(buf, count, &pos, entry->mem_file_buf,
40 entry->size);
41 }
42
mem_write(struct file * filp,struct kobject * kobj,const struct bin_attribute * bin_attr,char * buf,loff_t pos,size_t count)43 static ssize_t mem_write(struct file *filp, struct kobject *kobj,
44 const struct bin_attribute *bin_attr, char *buf, loff_t pos,
45 size_t count)
46 {
47 struct cbmem_entry *entry = to_cbmem_entry(kobj);
48
49 if (pos < 0 || pos >= entry->size)
50 return -EINVAL;
51 if (count > entry->size - pos)
52 count = entry->size - pos;
53
54 memcpy(entry->mem_file_buf + pos, buf, count);
55 return count;
56 }
57 static const BIN_ATTR_ADMIN_RW(mem, 0);
58
address_show(struct device * dev,struct device_attribute * attr,char * buf)59 static ssize_t address_show(struct device *dev, struct device_attribute *attr,
60 char *buf)
61 {
62 struct coreboot_device *cbdev = dev_to_coreboot_device(dev);
63
64 return sysfs_emit(buf, "0x%llx\n", cbdev->cbmem_entry.address);
65 }
66 static DEVICE_ATTR_RO(address);
67
size_show(struct device * dev,struct device_attribute * attr,char * buf)68 static ssize_t size_show(struct device *dev, struct device_attribute *attr,
69 char *buf)
70 {
71 struct coreboot_device *cbdev = dev_to_coreboot_device(dev);
72
73 return sysfs_emit(buf, "0x%x\n", cbdev->cbmem_entry.entry_size);
74 }
75 static DEVICE_ATTR_RO(size);
76
77 static struct attribute *attrs[] = {
78 &dev_attr_address.attr,
79 &dev_attr_size.attr,
80 NULL,
81 };
82
83 static const struct bin_attribute *const bin_attrs[] = {
84 &bin_attr_mem,
85 NULL,
86 };
87
88 static const struct attribute_group cbmem_entry_group = {
89 .attrs = attrs,
90 .bin_attrs = bin_attrs,
91 };
92
93 static const struct attribute_group *dev_groups[] = {
94 &cbmem_entry_group,
95 NULL,
96 };
97
cbmem_entry_probe(struct coreboot_device * dev)98 static int cbmem_entry_probe(struct coreboot_device *dev)
99 {
100 struct cbmem_entry *entry;
101
102 entry = devm_kzalloc(&dev->dev, sizeof(*entry), GFP_KERNEL);
103 if (!entry)
104 return -ENOMEM;
105
106 dev_set_drvdata(&dev->dev, entry);
107 entry->mem_file_buf = devm_memremap(&dev->dev, dev->cbmem_entry.address,
108 dev->cbmem_entry.entry_size,
109 MEMREMAP_WB);
110 if (IS_ERR(entry->mem_file_buf))
111 return PTR_ERR(entry->mem_file_buf);
112
113 entry->size = dev->cbmem_entry.entry_size;
114
115 return 0;
116 }
117
118 static const struct coreboot_device_id cbmem_ids[] = {
119 { .tag = LB_TAG_CBMEM_ENTRY },
120 { /* sentinel */ }
121 };
122 MODULE_DEVICE_TABLE(coreboot, cbmem_ids);
123
124 static struct coreboot_driver cbmem_entry_driver = {
125 .probe = cbmem_entry_probe,
126 .drv = {
127 .name = "cbmem",
128 .dev_groups = dev_groups,
129 },
130 .id_table = cbmem_ids,
131 };
132 module_coreboot_driver(cbmem_entry_driver);
133
134 MODULE_AUTHOR("Jack Rosenthal <jrosenth@chromium.org>");
135 MODULE_DESCRIPTION("Driver for exporting CBMEM entries in sysfs");
136 MODULE_LICENSE("GPL");
137