drivers/misc/tegra_timerinfo.c

/*
 * drivers/misc/tegra_timerinfo.c
 *
 * Copyright (c) 2012-2014, NVIDIA CORPORATION.  All rights reserved.
 *
 * Author:
 *	Jon Mayo <jmayo@nvidia.com>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/export.h>
#include <linux/module.h>
#include <linux/tegra-timer.h>

static int timerinfo_dev_mmap(struct file *file, struct vm_area_struct *vma);

static const struct file_operations timerinfo_dev_fops = {
	.owner = THIS_MODULE,
	.open = nonseekable_open,
	.mmap = timerinfo_dev_mmap,
	.llseek = noop_llseek,
};

static struct miscdevice timerinfo_dev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "timerinfo",
	.fops = &timerinfo_dev_fops,
};

static int timerinfo_dev_mmap(struct file *file, struct vm_area_struct *vma)
{
	/* start at first page containing TIMERUS_CNTR_1US */
	if (IS_ERR_OR_NULL(timer_reg_base_pa)) {
		pr_err("%s: Invalid timer_base_address\n", __func__);
		return -EINVAL;
	}

	if (vma->vm_end  - vma->vm_start != PAGE_SIZE)
		return -EINVAL;

	if (vma->vm_flags & VM_WRITE)
		return -EPERM;

	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

	if (remap_pfn_range(vma, vma->vm_start, timer_reg_base_pa >> PAGE_SHIFT,
						PAGE_SIZE, vma->vm_page_prot)) {
		pr_err("%s: remap_pfn_range failed\n", timerinfo_dev.name);
		return -EAGAIN;
	}

	return 0;
}

static int __init timerinfo_dev_init(void)
{
	return misc_register(&timerinfo_dev);
}

module_init(timerinfo_dev_init);
MODULE_LICENSE("GPL");