serial: 8250_aspeed_vuart: refactor sirq and lpc address setting code

This splits dedicated aspeed_vuart_set_{sirq,lpc_address}() functions
out of the sysfs store functions in preparation for adding DT
properties that will be poking the same registers.  While we're at it,
these functions now provide some basic bounds-checking on their
arguments.
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Link: https://lore.kernel.org/r/20210412034712.16778-3-zev@bewilderbeest.netSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_aspeed_vuart.c

@@ -72,22 +72,31 @@ static ssize_t lpc_address_show(struct device *dev,
 	return snprintf(buf, PAGE_SIZE - 1, "0x%x\n", addr);
 }
 
+static int aspeed_vuart_set_lpc_address(struct aspeed_vuart *vuart, u32 addr)
+{
+	if (addr > U16_MAX)
+		return -EINVAL;
+
+	writeb(addr >> 8, vuart->regs + ASPEED_VUART_ADDRH);
+	writeb(addr >> 0, vuart->regs + ASPEED_VUART_ADDRL);
+
+	return 0;
+}
+
 static ssize_t lpc_address_store(struct device *dev,
 				 struct device_attribute *attr,
 				 const char *buf, size_t count)
 {
 	struct aspeed_vuart *vuart = dev_get_drvdata(dev);
-	unsigned long val;
+	u32 val;
 	int err;
 
-	err = kstrtoul(buf, 0, &val);
+	err = kstrtou32(buf, 0, &val);
 	if (err)
 		return err;
 
-	writeb(val >> 8, vuart->regs + ASPEED_VUART_ADDRH);
-	writeb(val >> 0, vuart->regs + ASPEED_VUART_ADDRL);
-
-	return count;
+	err = aspeed_vuart_set_lpc_address(vuart, val);
+	return err ? : count;
 }
 
 static DEVICE_ATTR_RW(lpc_address);
@@ -105,27 +114,37 @@ static ssize_t sirq_show(struct device *dev,
 	return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg);
 }
 
+static int aspeed_vuart_set_sirq(struct aspeed_vuart *vuart, u32 sirq)
+{
+	u8 reg;
+
+	if (sirq > (ASPEED_VUART_GCRB_HOST_SIRQ_MASK >> ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT))
+		return -EINVAL;
+
+	sirq <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
+	sirq &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
+
+	reg = readb(vuart->regs + ASPEED_VUART_GCRB);
+	reg &= ~ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
+	reg |= sirq;
+	writeb(reg, vuart->regs + ASPEED_VUART_GCRB);
+
+	return 0;
+}
+
 static ssize_t sirq_store(struct device *dev, struct device_attribute *attr,
 			  const char *buf, size_t count)
 {
 	struct aspeed_vuart *vuart = dev_get_drvdata(dev);
 	unsigned long val;
 	int err;
-	u8 reg;
 
 	err = kstrtoul(buf, 0, &val);
 	if (err)
 		return err;
 
-	val <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
-	val &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
-
-	reg = readb(vuart->regs + ASPEED_VUART_GCRB);
-	reg &= ~ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
-	reg |= val;
-	writeb(reg, vuart->regs + ASPEED_VUART_GCRB);
-
-	return count;
+	err = aspeed_vuart_set_sirq(vuart, val);
+	return err ? : count;
 }
 
 static DEVICE_ATTR_RW(sirq);