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 27 static struct cbmem_entry *to_cbmem_entry(struct kobject *kobj) 28 { 29 return dev_get_drvdata(kobj_to_dev(kobj)); 30 } 31 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 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 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 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 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 const struct coreboot_device_id cbmem_ids[] = { 118 { .tag = LB_TAG_CBMEM_ENTRY }, 119 { /* sentinel */ } 120 }; 121 MODULE_DEVICE_TABLE(coreboot, cbmem_ids); 122 123 static struct coreboot_driver cbmem_entry_driver = { 124 .probe = cbmem_entry_probe, 125 .drv = { 126 .name = "cbmem", 127 .dev_groups = dev_groups, 128 }, 129 .id_table = cbmem_ids, 130 }; 131 module_coreboot_driver(cbmem_entry_driver); 132 133 MODULE_AUTHOR("Jack Rosenthal <jrosenth@chromium.org>"); 134 MODULE_DESCRIPTION("Driver for exporting CBMEM entries in sysfs"); 135 MODULE_LICENSE("GPL"); 136