#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include "linux_avm_helpers.h"

int avm_read_from_file(const char *filename, char *str, int maxlen)
{
	struct file *fp;
	mm_segment_t oldfs;
	int bytesRead;

	if(WARN_ON(!filename || !str || maxlen == 0))
		return -EINVAL;

	fp = filp_open(filename, O_RDONLY, 00);
	if (IS_ERR(fp) || (fp->f_op == 0)) {
		str[0] = 0;
		return -EIO;
	}
	/* Lesezugriff auf File(system) erlaubt? */
	if (fp->f_op->read == NULL) {
		str[0] = 0;
		filp_close(fp, NULL);
		return -EPERM;
	}
	oldfs = get_fs();
	set_fs(KERNEL_DS);
	fp->f_pos = 0; /* Von Anfang an lesen */
	bytesRead = fp->f_op->read(fp, str, maxlen - 1, &fp->f_pos);

	if (bytesRead < 0)
		bytesRead = 0;

	str[bytesRead] = 0;
	set_fs(oldfs);
	filp_close(fp, NULL); /* Close the file */
	return bytesRead;
}
EXPORT_SYMBOL(avm_read_from_file);

int avm_write_to_file(const char *filename, const char *str, int len)
{
	struct file *fp;
	mm_segment_t oldfs;

	if(WARN_ON(!filename || !str || len == 0))
		return -EINVAL;

	pr_debug("%s: write %s to %s\n", __func__, str, filename);
	fp = filp_open(filename, O_WRONLY, 00);

	if (IS_ERR(fp) || (fp->f_op == 0))
		return -EIO;

	/* Schreibzugriff auf File(system) erlaubt? */
	if (fp->f_op->write == NULL) {
		pr_err("[avm_power]speedstep failed: write %s\n",
			   filename);
		filp_close(fp, NULL);
		return -EPERM;
	}
	oldfs = get_fs();
	set_fs(KERNEL_DS);
	fp->f_pos = 0; /* Von Anfang an schreiben*/
	fp->f_op->write(fp, str, len, &fp->f_pos);
	set_fs(oldfs);
	filp_close(fp, NULL); /* Close the file */
	return 0;
}
EXPORT_SYMBOL(avm_write_to_file);

/*
 * Sometimes avm modules need symbols that are not exported by the kernel.
 *
 * To avoid the need to patch every kernel there is, we just export them
 * here. Use the GPL variant unless the exported symbol is known to be non-GPL.
 */
EXPORT_SYMBOL_GPL(func_ptr_is_kernel_text);