[v3] usb: clean up some of the computations in adu_read

Commit Message

dmg June 21, 2019, 3:22 p.m. UTC

From: Daniel M German <[e-mail]>

Replace ?: with min to calculate the number of bytes in the secondary buffer,
including changing the data type of data_in_secondary to size_t to be
type-consistent. data_in_secondary can never be negative.

Remove some spurious calculations (copy_to_user returns zero on success),
making one variable redundant (i)

This change does not alter the functionality of the code.

Signed-off-by: Daniel M German <[e-mail]>
---
Changes from v1:

        - Replace %d modifier with %zu to avoid compilation warning
        - Note that v2 was not properly labeled (its subject was [PATCH])
          v2 and v3 are identical in content.
        
---
 drivers/usb/misc/adutux.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

Comments

dmg June 21, 2019, 3:55 p.m. UTC | #1

[e-mail] writes:

> From: Daniel M German <[e-mail]>
>

Sorry, I put a spurious line in the body of the email. I am resending.

--dmg

Patch

diff --git a/drivers/usb/misc/adutux.c b/drivers/usb/misc/adutux.c
index 9465fb95d70a..344d523b0502 100644
--- a/drivers/usb/misc/adutux.c
+++ b/drivers/usb/misc/adutux.c
@@ -343,7 +343,6 @@  static ssize_t adu_read(struct file *file, __user char *buffer, size_t count,
 	struct adu_device *dev;
 	size_t bytes_read = 0;
 	size_t bytes_to_read = count;
-	int i;
 	int retval = 0;
 	int timeout = 0;
 	int should_submit = 0;
@@ -371,23 +370,22 @@  static ssize_t adu_read(struct file *file, __user char *buffer, size_t count,
 	timeout = COMMAND_TIMEOUT;
 	dev_dbg(&dev->udev->dev, "%s : about to start looping\n", __func__);
 	while (bytes_to_read) {
-		int data_in_secondary = dev->secondary_tail - dev->secondary_head;
+		size_t data_in_secondary = dev->secondary_tail - dev->secondary_head;
 		dev_dbg(&dev->udev->dev,
-			"%s : while, data_in_secondary=%d, status=%d\n",
+			"%s : while, data_in_secondary=%zu, status=%d\n",
 			__func__, data_in_secondary,
 			dev->interrupt_in_urb->status);
 
 		if (data_in_secondary) {
 			/* drain secondary buffer */
-			int amount = bytes_to_read < data_in_secondary ? bytes_to_read : data_in_secondary;
-			i = copy_to_user(buffer, dev->read_buffer_secondary+dev->secondary_head, amount);
-			if (i) {
+			size_t amount = min(bytes_to_read, data_in_secondary);
+			if (copy_to_user(buffer, dev->read_buffer_secondary+dev->secondary_head, amount)) {
 				retval = -EFAULT;
 				goto exit;
 			}
-			dev->secondary_head += (amount - i);
-			bytes_read += (amount - i);
-			bytes_to_read -= (amount - i);
+			dev->secondary_head += amount;
+			bytes_read += amount;
+			bytes_to_read -= amount;
 		} else {
 			/* we check the primary buffer */
 			spin_lock_irqsave (&dev->buflock, flags);