[PATCH] USB: optimise devio.c::usbdev_read

this is a small optimisation. It is ridiculous to do a kmalloc for
18 bytes. This puts it onto the stack.

Signed-off-by: Oliver Neukum <oliver@neukum.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 8 insertions, 13 deletions

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 2b68998fe4b3..d01bd77e7b14 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -134,26 +134,21 @@ static ssize_t usbdev_read(struct file *file, char __user *buf, size_t nbytes, l
 	}
 
 	if (pos < sizeof(struct usb_device_descriptor)) {
-		struct usb_device_descriptor *desc = kmalloc(sizeof(*desc), GFP_KERNEL);
-		if (!desc) {
-			ret = -ENOMEM;
-			goto err;
-		}
-		memcpy(desc, &dev->descriptor, sizeof(dev->descriptor));
-		le16_to_cpus(&desc->bcdUSB);
-		le16_to_cpus(&desc->idVendor);
-		le16_to_cpus(&desc->idProduct);
-		le16_to_cpus(&desc->bcdDevice);
+		struct usb_device_descriptor temp_desc ; /* 18 bytes - fits on the stack */
+
+		memcpy(&temp_desc, &dev->descriptor, sizeof(dev->descriptor));
+		le16_to_cpus(&temp_desc->bcdUSB);
+		le16_to_cpus(&temp_desc->idVendor);
+		le16_to_cpus(&temp_desc->idProduct);
+		le16_to_cpus(&temp_desc->bcdDevice);
 
 		len = sizeof(struct usb_device_descriptor) - pos;
 		if (len > nbytes)
 			len = nbytes;
-		if (copy_to_user(buf, ((char *)desc) + pos, len)) {
-			kfree(desc);
+		if (copy_to_user(buf, ((char *)&temp_desc) + pos, len)) {
 			ret = -EFAULT;
 			goto err;
 		}
-		kfree(desc);
 
 		*ppos += len;
 		buf += len;