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 struct coreboot_driver cbmem_entry_driver = {
118 	.probe = cbmem_entry_probe,
119 	.drv = {
120 		.name = "cbmem",
121 		.owner = THIS_MODULE,
122 		.dev_groups = dev_groups,
123 	},
124 	.tag = LB_TAG_CBMEM_ENTRY,
125 };
126 module_coreboot_driver(cbmem_entry_driver);
127 
128 MODULE_AUTHOR("Jack Rosenthal <jrosenth@chromium.org>");
129 MODULE_LICENSE("GPL");
130