From linux-usb-devel-admin@lists.sourceforge.net Fri Jan 6 12:51:44 2006 From: Oliver Neukum To: Pete Zaitcev Subject: USB: optimise devio.c::usbdev_read Cc: gregkh@suse.de Content-Disposition: inline Message-Id: <200601062124.25970.oliver@neukum.org> Date: Fri, 6 Jan 2006 21:24:25 +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 Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/devio.c | 21 ++++++++------------- 1 file changed, 8 insertions(+), 13 deletions(-) --- gregkh-2.6.orig/drivers/usb/core/devio.c +++ gregkh-2.6/drivers/usb/core/devio.c @@ -134,26 +134,21 @@ static ssize_t usbdev_read(struct file * } 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;