[PATCH] USB: optimise devio.c::usbdev_read
Oliver Neukum [Fri, 6 Jan 2006 20:24:25 +0000 (21:24 +0100)]
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>

drivers/usb/core/devio.c

index 2b68998..d01bd77 100644 (file)
@@ -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;