video/via: Convert to kstrtou8_from_user

This patch replaces the code for getting an number from a
userspace buffer by a simple call to kstrou8_from_user.
This makes it easier to read and less error prone.
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Acked-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>

drivers/video/via/viafbdev.c

@@ -1276,17 +1276,12 @@ static int viafb_dfph_proc_open(struct inode *inode, struct file *file)
 static ssize_t viafb_dfph_proc_write(struct file *file,
 	const char __user *buffer, size_t count, loff_t *pos)
 {
-	char buf[20];
-	u8 reg_val = 0;
-	unsigned long length;
-	if (count < 1)
-		return -EINVAL;
-	length = count > 20 ? 20 : count;
-	if (copy_from_user(&buf[0], buffer, length))
-		return -EFAULT;
-	buf[length - 1] = '\0';	/*Ensure end string */
-	if (kstrtou8(buf, 0, &reg_val) < 0)
-		return -EINVAL;
+	int err;
+	u8 reg_val;
+	err = kstrtou8_from_user(buffer, count, 0, &reg_val);
+	if (err)
+		return err;
+
 	viafb_write_reg_mask(CR97, VIACR, reg_val, 0x0f);
 	return count;
 }
@@ -1316,17 +1311,12 @@ static int viafb_dfpl_proc_open(struct inode *inode, struct file *file)
 static ssize_t viafb_dfpl_proc_write(struct file *file,
 	const char __user *buffer, size_t count, loff_t *pos)
 {
-	char buf[20];
-	u8 reg_val = 0;
-	unsigned long length;
-	if (count < 1)
-		return -EINVAL;
-	length = count > 20 ? 20 : count;
-	if (copy_from_user(&buf[0], buffer, length))
-		return -EFAULT;
-	buf[length - 1] = '\0';	/*Ensure end string */
-	if (kstrtou8(buf, 0, &reg_val) < 0)
-		return -EINVAL;
+	int err;
+	u8 reg_val;
+	err = kstrtou8_from_user(buffer, count, 0, &reg_val);
+	if (err)
+		return err;
+
 	viafb_write_reg_mask(CR99, VIACR, reg_val, 0x0f);
 	return count;
 }