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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
23struct cbmem_entry {
24 char *mem_file_buf;
25 u32 size;
26};
27
28static struct cbmem_entry *to_cbmem_entry(struct kobject *kobj)
29{
30 return dev_get_drvdata(kobj_to_dev(kobj));
31}
32
33static 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
43static 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}
57static const BIN_ATTR_ADMIN_RW(mem, 0);
58
59static 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}
66static DEVICE_ATTR_RO(address);
67
68static 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}
75static DEVICE_ATTR_RO(size);
76
77static struct attribute *attrs[] = {
78 &dev_attr_address.attr,
79 &dev_attr_size.attr,
80 NULL,
81};
82
83static const struct bin_attribute *const bin_attrs[] = {
84 &bin_attr_mem,
85 NULL,
86};
87
88static const struct attribute_group cbmem_entry_group = {
89 .attrs = attrs,
90 .bin_attrs = bin_attrs,
91};
92
93static const struct attribute_group *dev_groups[] = {
94 &cbmem_entry_group,
95 NULL,
96};
97
98static 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
118static const struct coreboot_device_id cbmem_ids[] = {
119 { .tag = LB_TAG_CBMEM_ENTRY },
120 { /* sentinel */ }
121};
122MODULE_DEVICE_TABLE(coreboot, cbmem_ids);
123
124static 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};
132module_coreboot_driver(cbmem_entry_driver);
133
134MODULE_AUTHOR("Jack Rosenthal <[email protected]>");
135MODULE_DESCRIPTION("Driver for exporting CBMEM entries in sysfs");
136MODULE_LICENSE("GPL");