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
22struct cbmem_entry {
23	char *mem_file_buf;
24	u32 size;
25};
26
27static struct cbmem_entry *to_cbmem_entry(struct kobject *kobj)
28{
29	return dev_get_drvdata(kobj_to_dev(kobj));
30}
31
32static 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
42static 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}
56static BIN_ATTR_ADMIN_RW(mem, 0);
57
58static 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}
65static DEVICE_ATTR_RO(address);
66
67static 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}
74static DEVICE_ATTR_RO(size);
75
76static struct attribute *attrs[] = {
77	&dev_attr_address.attr,
78	&dev_attr_size.attr,
79	NULL,
80};
81
82static struct bin_attribute *bin_attrs[] = {
83	&bin_attr_mem,
84	NULL,
85};
86
87static const struct attribute_group cbmem_entry_group = {
88	.attrs = attrs,
89	.bin_attrs = bin_attrs,
90};
91
92static const struct attribute_group *dev_groups[] = {
93	&cbmem_entry_group,
94	NULL,
95};
96
97static 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
117static const struct coreboot_device_id cbmem_ids[] = {
118	{ .tag = LB_TAG_CBMEM_ENTRY },
119	{ /* sentinel */ }
120};
121MODULE_DEVICE_TABLE(coreboot, cbmem_ids);
122
123static struct coreboot_driver cbmem_entry_driver = {
124	.probe = cbmem_entry_probe,
125	.drv = {
126		.name = "cbmem",
127		.owner = THIS_MODULE,
128		.dev_groups = dev_groups,
129	},
130	.id_table = cbmem_ids,
131};
132module_coreboot_driver(cbmem_entry_driver);
133
134MODULE_AUTHOR("Jack Rosenthal <jrosenth@chromium.org>");
135MODULE_LICENSE("GPL");
136