[PATCH 4/7] char: xillybus: Use unsigned arithmetic for jiffies differences

[Eli Billauer]

Change the type of jiffies-related deadline variables from long to
unsigned long, and remove unnecessary casts when computing time
remaining as deadline - jiffies.

No functional change is expected: although signed overflow is undefined
in the C standard, processors perform the calculation correctly in
practice. Using unsigned arithmetic is nevertheless the proper way to
handle jiffies differences.

Signed-off-by: Eli Billauer <eli.billauer@xxxxxxxxx>
---
 drivers/char/xillybus/xillybus_core.c |  5 +++--
 drivers/char/xillybus/xillyusb.c      | 17 ++++++++++-------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/char/xillybus/xillybus_core.c b/drivers/char/xillybus/xillybus_core.c
index 952ef149aba1..7acebc1e6050 100644
--- a/drivers/char/xillybus/xillybus_core.c
+++ b/drivers/char/xillybus/xillybus_core.c
@@ -694,7 +694,8 @@ static ssize_t xillybus_read(struct file *filp, char __user *userbuf,
 	unsigned long flags;
 	int bytes_done = 0;
 	int no_time_left = 0;
-	long deadline, left_to_sleep;
+	unsigned long deadline;
+	long left_to_sleep;
 	struct xilly_channel *channel = filp->private_data;
 
 	int empty, reached_eof, exhausted, ready;
@@ -938,7 +939,7 @@ static ssize_t xillybus_read(struct file *filp, char __user *userbuf,
 			return -EINTR;
 		}
 
-		left_to_sleep = deadline - ((long) jiffies);
+		left_to_sleep = deadline - jiffies;
 
 		/*
 		 * If our time is out, skip the waiting. We may miss wr_sleepy
diff --git a/drivers/char/xillybus/xillyusb.c b/drivers/char/xillybus/xillyusb.c
index 7d2434c02fa7..aa08206a18ef 100644
--- a/drivers/char/xillybus/xillyusb.c
+++ b/drivers/char/xillybus/xillyusb.c
@@ -1127,12 +1127,13 @@ static int xillyusb_send_opcode(struct xillyusb_dev *xdev,
  */
 
 static int flush_downstream(struct xillyusb_channel *chan,
-			    long timeout,
+			    unsigned long timeout,
 			    bool interruptible)
 {
 	struct xillyusb_dev *xdev = chan->xdev;
 	int chan_num = chan->chan_idx << 1;
-	long deadline, left_to_sleep;
+	unsigned long deadline;
+	long left_to_sleep;
 	int rc;
 
 	if (chan->flushed)
@@ -1141,7 +1142,8 @@ static int flush_downstream(struct xillyusb_channel *chan,
 	deadline = jiffies + 1 + timeout;
 
 	if (chan->flushing) {
-		long cancel_deadline = jiffies + 1 + XILLY_RESPONSE_TIMEOUT;
+		unsigned long cancel_deadline =
+			jiffies + 1 + XILLY_RESPONSE_TIMEOUT;
 
 		chan->canceled = 0;
 		rc = xillyusb_send_opcode(xdev, chan_num,
@@ -1152,7 +1154,7 @@ static int flush_downstream(struct xillyusb_channel *chan,
 
 		/* Ignoring interrupts. Cancellation must be handled */
 		while (!chan->canceled) {
-			left_to_sleep = cancel_deadline - ((long)jiffies);
+			left_to_sleep = cancel_deadline - jiffies;
 
 			if (left_to_sleep <= 0) {
 				report_io_error(xdev, -EIO);
@@ -1202,7 +1204,7 @@ static int flush_downstream(struct xillyusb_channel *chan,
 	}
 
 	while (chan->flushing) {
-		left_to_sleep = deadline - ((long)jiffies);
+		left_to_sleep = deadline - jiffies;
 
 		if (left_to_sleep <= 0)
 			return -ETIMEDOUT;
@@ -1435,7 +1437,8 @@ static ssize_t xillyusb_read(struct file *filp, char __user *userbuf,
 	struct xillyfifo *fifo = chan->in_fifo;
 	int chan_num = (chan->chan_idx << 1) | 1;
 
-	long deadline, left_to_sleep;
+	unsigned long deadline;
+	long left_to_sleep;
 	int bytes_done = 0;
 	bool sent_set_push = false;
 	int rc;
@@ -1464,7 +1467,7 @@ static ssize_t xillyusb_read(struct file *filp, char __user *userbuf,
 		bytes_done += rc;
 		chan->in_consumed_bytes += rc;
 
-		left_to_sleep = deadline - ((long)jiffies);
+		left_to_sleep = deadline - jiffies;
 
 		/*
 		 * Some 32-bit arithmetic that may wrap. Note that
-- 
2.34.1