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 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};
126module_coreboot_driver(cbmem_entry_driver);
127
128MODULE_AUTHOR("Jack Rosenthal <jrosenth@chromium.org>");
129MODULE_LICENSE("GPL");