--- /dev/null
+/*
+ * dmi-sysfs.c
+ *
+ * This module exports the DMI tables read-only to userspace through the
+ * sysfs file system.
+ *
+ * Data is currently found below
+ * /sys/firmware/dmi/...
+ *
+ * DMI attributes are presented in attribute files with names
+ * formatted using %d-%d, so that the first integer indicates the
+ * structure type (0-255), and the second field is the instance of that
+ * entry.
+ *
+ * Copyright 2011 Google, Inc.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kobject.h>
+#include <linux/dmi.h>
+#include <linux/capability.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/io.h>
+
+#define MAX_ENTRY_TYPE 255 /* Most of these aren't used, but we consider
+ the top entry type is only 8 bits */
+
+struct dmi_sysfs_entry {
+ struct dmi_header dh;
+ struct kobject kobj;
+ int instance;
+ int position;
+ struct list_head list;
+};
+
+/*
+ * Global list of dmi_sysfs_entry. Even though this should only be
+ * manipulated at setup and teardown, the lazy nature of the kobject
+ * system means we get lazy removes.
+ */
+static LIST_HEAD(entry_list);
+static DEFINE_SPINLOCK(entry_list_lock);
+
+/* dmi_sysfs_attribute - Top level attribute. used by all entries. */
+struct dmi_sysfs_attribute {
+ struct attribute attr;
+ ssize_t (*show)(struct dmi_sysfs_entry *entry, char *buf);
+};
+
+#define DMI_SYSFS_ATTR(_entry, _name) \
+struct dmi_sysfs_attribute dmi_sysfs_attr_##_entry##_##_name = { \
+ .attr = {.name = __stringify(_name), .mode = 0400}, \
+ .show = dmi_sysfs_##_entry##_##_name, \
+}
+
+/*
+ * dmi_sysfs_mapped_attribute - Attribute where we require the entry be
+ * mapped in. Use in conjunction with dmi_sysfs_specialize_attr_ops.
+ */
+struct dmi_sysfs_mapped_attribute {
+ struct attribute attr;
+ ssize_t (*show)(struct dmi_sysfs_entry *entry,
+ const struct dmi_header *dh,
+ char *buf);
+};
+
+#define DMI_SYSFS_MAPPED_ATTR(_entry, _name) \
+struct dmi_sysfs_mapped_attribute dmi_sysfs_attr_##_entry##_##_name = { \
+ .attr = {.name = __stringify(_name), .mode = 0400}, \
+ .show = dmi_sysfs_##_entry##_##_name, \
+}
+
+/*************************************************
+ * Generic DMI entry support.
+ *************************************************/
+
+static struct dmi_sysfs_entry *to_entry(struct kobject *kobj)
+{
+ return container_of(kobj, struct dmi_sysfs_entry, kobj);
+}
+
+static struct dmi_sysfs_attribute *to_attr(struct attribute *attr)
+{
+ return container_of(attr, struct dmi_sysfs_attribute, attr);
+}
+
+static ssize_t dmi_sysfs_attr_show(struct kobject *kobj,
+ struct attribute *_attr, char *buf)
+{
+ struct dmi_sysfs_entry *entry = to_entry(kobj);
+ struct dmi_sysfs_attribute *attr = to_attr(_attr);
+
+ /* DMI stuff is only ever admin visible */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EACCES;
+
+ return attr->show(entry, buf);
+}
+
+static const struct sysfs_ops dmi_sysfs_attr_ops = {
+ .show = dmi_sysfs_attr_show,
+};
+
+typedef ssize_t (*dmi_callback)(struct dmi_sysfs_entry *,
+ const struct dmi_header *dh, void *);
+
+struct find_dmi_data {
+ struct dmi_sysfs_entry *entry;
+ dmi_callback callback;
+ void *private;
+ int instance_countdown;
+ ssize_t ret;
+};
+
+static void find_dmi_entry_helper(const struct dmi_header *dh,
+ void *_data)
+{
+ struct find_dmi_data *data = _data;
+ struct dmi_sysfs_entry *entry = data->entry;
+
+ /* Is this the entry we want? */
+ if (dh->type != entry->dh.type)
+ return;
+
+ if (data->instance_countdown != 0) {
+ /* try the next instance? */
+ data->instance_countdown--;
+ return;
+ }
+
+ /*
+ * Don't ever revisit the instance. Short circuit later
+ * instances by letting the instance_countdown run negative
+ */
+ data->instance_countdown--;
+
+ /* Found the entry */
+ data->ret = data->callback(entry, dh, data->private);
+}
+
+/* State for passing the read parameters through dmi_find_entry() */
+struct dmi_read_state {
+ char *buf;
+ loff_t pos;
+ size_t count;
+};
+
+static ssize_t find_dmi_entry(struct dmi_sysfs_entry *entry,
+ dmi_callback callback, void *private)
+{
+ struct find_dmi_data data = {
+ .entry = entry,
+ .callback = callback,
+ .private = private,
+ .instance_countdown = entry->instance,
+ .ret = -EIO, /* To signal the entry disappeared */
+ };
+ int ret;
+
+ ret = dmi_walk(find_dmi_entry_helper, &data);
+ /* This shouldn't happen, but just in case. */
+ if (ret)
+ return -EINVAL;
+ return data.ret;
+}
+
+/*
+ * Calculate and return the byte length of the dmi entry identified by
+ * dh. This includes both the formatted portion as well as the
+ * unformatted string space, including the two trailing nul characters.
+ */
+static size_t dmi_entry_length(const struct dmi_header *dh)
+{
+ const char *p = (const char *)dh;
+
+ p += dh->length;
+
+ while (p[0] || p[1])
+ p++;
+
+ return 2 + p - (const char *)dh;
+}
+
+/*************************************************
+ * Generic DMI entry support.
+ *************************************************/
+
+static ssize_t dmi_sysfs_entry_length(struct dmi_sysfs_entry *entry, char *buf)
+{
+ return sprintf(buf, "%d\n", entry->dh.length);
+}
+
+static ssize_t dmi_sysfs_entry_handle(struct dmi_sysfs_entry *entry, char *buf)
+{
+ return sprintf(buf, "%d\n", entry->dh.handle);
+}
+
+static ssize_t dmi_sysfs_entry_type(struct dmi_sysfs_entry *entry, char *buf)
+{
+ return sprintf(buf, "%d\n", entry->dh.type);
+}
+
+static ssize_t dmi_sysfs_entry_instance(struct dmi_sysfs_entry *entry,
+ char *buf)
+{
+ return sprintf(buf, "%d\n", entry->instance);
+}
+
+static ssize_t dmi_sysfs_entry_position(struct dmi_sysfs_entry *entry,
+ char *buf)
+{
+ return sprintf(buf, "%d\n", entry->position);
+}
+
+static DMI_SYSFS_ATTR(entry, length);
+static DMI_SYSFS_ATTR(entry, handle);
+static DMI_SYSFS_ATTR(entry, type);
+static DMI_SYSFS_ATTR(entry, instance);
+static DMI_SYSFS_ATTR(entry, position);
+
+static struct attribute *dmi_sysfs_entry_attrs[] = {
+ &dmi_sysfs_attr_entry_length.attr,
+ &dmi_sysfs_attr_entry_handle.attr,
+ &dmi_sysfs_attr_entry_type.attr,
+ &dmi_sysfs_attr_entry_instance.attr,
+ &dmi_sysfs_attr_entry_position.attr,
+ NULL,
+};
+
+static ssize_t dmi_entry_raw_read_helper(struct dmi_sysfs_entry *entry,
+ const struct dmi_header *dh,
+ void *_state)
+{
+ struct dmi_read_state *state = _state;
+ size_t entry_length;
+
+ entry_length = dmi_entry_length(dh);
+
+ return memory_read_from_buffer(state->buf, state->count,
+ &state->pos, dh, entry_length);
+}
+
+static ssize_t dmi_entry_raw_read(struct file *filp,
+ struct kobject *kobj,
+ struct bin_attribute *bin_attr,
+ char *buf, loff_t pos, size_t count)
+{
+ struct dmi_sysfs_entry *entry = to_entry(kobj);
+ struct dmi_read_state state = {
+ .buf = buf,
+ .pos = pos,
+ .count = count,
+ };
+
+ return find_dmi_entry(entry, dmi_entry_raw_read_helper, &state);
+}
+
+static const struct bin_attribute dmi_entry_raw_attr = {
+ .attr = {.name = "raw", .mode = 0400},
+ .read = dmi_entry_raw_read,
+};
+
+static void dmi_sysfs_entry_release(struct kobject *kobj)
+{
+ struct dmi_sysfs_entry *entry = to_entry(kobj);
+ sysfs_remove_bin_file(&entry->kobj, &dmi_entry_raw_attr);
+ spin_lock(&entry_list_lock);
+ list_del(&entry->list);
+ spin_unlock(&entry_list_lock);
+ kfree(entry);
+}
+
+static struct kobj_type dmi_sysfs_entry_ktype = {
+ .release = dmi_sysfs_entry_release,
+ .sysfs_ops = &dmi_sysfs_attr_ops,
+ .default_attrs = dmi_sysfs_entry_attrs,
+};
+
+static struct kobject *dmi_kobj;
+static struct kset *dmi_kset;
+
+/* Global count of all instances seen. Only for setup */
+static int __initdata instance_counts[MAX_ENTRY_TYPE + 1];
+
+/* Global positional count of all entries seen. Only for setup */
+static int __initdata position_count;
+
+static void __init dmi_sysfs_register_handle(const struct dmi_header *dh,
+ void *_ret)
+{
+ struct dmi_sysfs_entry *entry;
+ int *ret = _ret;
+
+ /* If a previous entry saw an error, short circuit */
+ if (*ret)
+ return;
+
+ /* Allocate and register a new entry into the entries set */
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry) {
+ *ret = -ENOMEM;
+ return;
+ }
+
+ /* Set the key */
+ entry->dh = *dh;
+ entry->instance = instance_counts[dh->type]++;
+ entry->position = position_count++;
+
+ entry->kobj.kset = dmi_kset;
+ *ret = kobject_init_and_add(&entry->kobj, &dmi_sysfs_entry_ktype, NULL,
+ "%d-%d", dh->type, entry->instance);
+
+ if (*ret) {
+ kfree(entry);
+ return;
+ }
+
+ /* Thread on the global list for cleanup */
+ spin_lock(&entry_list_lock);
+ list_add_tail(&entry->list, &entry_list);
+ spin_unlock(&entry_list_lock);
+
+ /* Create the raw binary file to access the entry */
+ *ret = sysfs_create_bin_file(&entry->kobj, &dmi_entry_raw_attr);
+ if (*ret)
+ goto out_err;
+
+ return;
+out_err:
+ kobject_put(&entry->kobj);
+ return;
+}
+
+static void cleanup_entry_list(void)
+{
+ struct dmi_sysfs_entry *entry, *next;
+
+ /* No locks, we are on our way out */
+ list_for_each_entry_safe(entry, next, &entry_list, list) {
+ kobject_put(&entry->kobj);
+ }
+}
+
+static int __init dmi_sysfs_init(void)
+{
+ int error = -ENOMEM;
+ int val;
+
+ /* Set up our directory */
+ dmi_kobj = kobject_create_and_add("dmi", firmware_kobj);
+ if (!dmi_kobj)
+ goto err;
+
+ dmi_kset = kset_create_and_add("entries", NULL, dmi_kobj);
+ if (!dmi_kset)
+ goto err;
+
+ val = 0;
+ error = dmi_walk(dmi_sysfs_register_handle, &val);
+ if (error)
+ goto err;
+ if (val) {
+ error = val;
+ goto err;
+ }
+
+ pr_debug("dmi-sysfs: loaded.\n");
+
+ return 0;
+err:
+ cleanup_entry_list();
+ kset_unregister(dmi_kset);
+ kobject_put(dmi_kobj);
+ return error;
+}
+
+/* clean up everything. */
+static void __exit dmi_sysfs_exit(void)
+{
+ pr_debug("dmi-sysfs: unloading.\n");
+ cleanup_entry_list();
+ kset_unregister(dmi_kset);
+ kobject_put(dmi_kobj);
+}
+
+module_init(dmi_sysfs_init);
+module_exit(dmi_sysfs_exit);
+
+MODULE_AUTHOR("Mike Waychison <mikew@google.com>");
+MODULE_DESCRIPTION("DMI sysfs support");
+MODULE_LICENSE("GPL");
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff