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/mod_devicetable.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 28 static struct cbmem_entry *to_cbmem_entry(struct kobject *kobj) 29 { 30 return dev_get_drvdata(kobj_to_dev(kobj)); 31 } 32 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 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 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 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 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