drivers/firmware/google/cbmem.c

   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");