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[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>
This commit is contained in:
Oliver Neukum 2006-01-06 21:24:25 +01:00 committed by Greg Kroah-Hartman
parent 60f780528f
commit 8781ba0aa9
1 changed files with 8 additions and 13 deletions
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21
drivers/usb/core/devio.c
View 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;