Linux C HexString轉Hex

#include <linux/ctype.h>

static int oneHexChar2Hex(char Hex)
{
	int outHex = 0;
	if(isdigit(hex)){
		outHex = hex - '0';
	}else if(isupper(hex)){
		outHex = hex - 'A' + 10;
	}else{
		outHex = hex - 'a' + 10;
	}
	return outHex;
}

static int HexString2Hex(char *inHexString,char outHex,int count)
{
	int ret = -1;
	int len = 0;
	int i;
	char ch1 ch2;

	if((NULL == inHexString) || (NULL == outHex))
		break;
	len  = count;
	if(len < 1)
		break;
	len &= ~1;
	for(i = 0; i < len; i+=2){
		ch1 = inHexString[i];
		ch2 = inHexString[i+1];
		outHex[i/2+1] = 0;
		if(isxdigit(ch1) && isxdigit(ch2)){
			ch1 = oneHexChar2Hex(ch1);
			ch2 = oneHexChar2Hex(ch2);
			outHex[i/2] = (ch1 << 4)| ch2;
		}else{
			printk("err: %c or %c is not hex digit!\n",ch1,ch2);
			goto EXIT;
		}
	}
	return 0;
EXIT:
	return ret;
}

/*
 * For Linux driver attr file debug interface
*/
static ssize_t dumpRegister_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	snprintf(buf,"%s\n","nothing");
	return strlen(buf);
}

/*
 * echo 00 > register  : dump bank0 register value;
 * echo 01 > register  : dump bank1 register value;
 * echo 0001 > register : read bank0 register-0x01 value
 * echo 0001ff > register : write bank0 register-0x01  value:0xff
*/
static ssize_t dumpRegister_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
	int value = 0;
	int len;
	int i;
	unsigned char out[8];
	
	len = strlen(buf);
	if(len < 2)
		return count;
		
	HexString2Hex(buf,out,len);
	
	switch(len){
		case 3://dump register value
			i2c_write_byte(0xff,out[0]&0xff);
			for(i=0;i<256;i++){
				if(i%16 == 0)
					printk("\n");
				printk("0x%2x ", i2c_read_byte(i&0xff));
			}
			break;
		case 5:
			break;
		case 7: //write register value
			i2c_write_byte(0xff,out[0]&0xff);
			i2c_write_byte(out[1]&0xff,out[2]&0xff);
			break;
		default:
			break;
	}
}
static DEVICE_ATTR(register,S_IRUGO | S_IWUSR, dumpRegister_show,dumpRegister_store)

static int xxx_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
	...
	...
	if(device_create_file(&client->dev,&dev_attr_register)){
		printk("create dev_attr_register failed.\n");
	}
}