drivers/firmware/google/memconsole.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * memconsole.c
 *
 * Architecture-independent parts of the memory based BIOS console.
 *
 * Copyright 2017 Google Inc.
 */

#include <linux/sysfs.h>
#include <linux/kobject.h>
#include <linux/module.h>

#include "memconsole.h"

static ssize_t memconsole_read(struct file *filp, struct kobject *kobp,
			       struct bin_attribute *bin_attr, char *buf,
			       loff_t pos, size_t count)
{
	ssize_t (*memconsole_read_func)(char *, loff_t, size_t);

	memconsole_read_func = bin_attr->private;
	if (WARN_ON_ONCE(!memconsole_read_func))
		return -EIO;

	return memconsole_read_func(buf, pos, count);
}

static struct bin_attribute memconsole_bin_attr = {
	.attr = {.name = "log", .mode = 0444},
	.read = memconsole_read,
};

void memconsole_setup(ssize_t (*read_func)(char *, loff_t, size_t))
{
	memconsole_bin_attr.private = read_func;
}
EXPORT_SYMBOL(memconsole_setup);

int memconsole_sysfs_init(void)
{
	return sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr);
}
EXPORT_SYMBOL(memconsole_sysfs_init);

void memconsole_exit(void)
{
	sysfs_remove_bin_file(firmware_kobj, &memconsole_bin_attr);
}
EXPORT_SYMBOL(memconsole_exit);

MODULE_AUTHOR("Google, Inc.");
MODULE_DESCRIPTION("Architecture-independent parts of the memory based BIOS console");
MODULE_LICENSE("GPL");