In some functions in drivers/usb/core/message.c kmalloc is used to
allocate fix size of memory chunks; and the chunks is freed at the end
of each functions. The sizes are not so large: 8(struct
usb_ctrlrequest), 18(struct usb_device_descriptor), and 2(u16) bytes.
I wonder why the invocations of kmalloc are needed in these functions.
Following patch is for avoiding invocations of kmalloc. Instead stacks
are used.
The patch is generated by co-diff against
rsync://kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
Signed-off-by: Masatake YAMATO <[email protected]>
Index: drivers/usb/core/message.c
===================================================================
--- 6f51e67e4a433ee0ff866a6ac18a4bce798fe0c7/drivers/usb/core/message.c (mode:100644)
+++ uncommitted/drivers/usb/core/message.c (mode:100644)
@@ -142,11 +142,9 @@
int usb_control_msg(struct usb_device *dev, unsigned int pipe, __u8 request, __u8 requesttype,
__u16 value, __u16 index, void *data, __u16 size, int timeout)
{
- struct usb_ctrlrequest *dr = kmalloc(sizeof(struct usb_ctrlrequest), GFP_NOIO);
+ struct usb_ctrlrequest dr_rec;
+ struct usb_ctrlrequest *dr = &dr_rec;
int ret;
-
- if (!dr)
- return -ENOMEM;
dr->bRequestType= requesttype;
dr->bRequest = request;
@@ -158,7 +156,6 @@
ret = usb_internal_control_msg(dev, pipe, dr, data, size, timeout);
- kfree(dr);
return ret;
}
@@ -794,19 +791,17 @@
*/
int usb_get_device_descriptor(struct usb_device *dev, unsigned int size)
{
+ struct usb_device_descriptor desc_rec;
struct usb_device_descriptor *desc;
int ret;
if (size > sizeof(*desc))
return -EINVAL;
- desc = kmalloc(sizeof(*desc), GFP_NOIO);
- if (!desc)
- return -ENOMEM;
+ desc = &desc_rec;
ret = usb_get_descriptor(dev, USB_DT_DEVICE, 0, desc, size);
if (ret >= 0)
memcpy(&dev->descriptor, desc, size);
- kfree(desc);
return ret;
}
@@ -835,17 +830,13 @@
int usb_get_status(struct usb_device *dev, int type, int target, void *data)
{
int ret;
- u16 *status = kmalloc(sizeof(*status), GFP_KERNEL);
-
- if (!status)
- return -ENOMEM;
+ u16 status;
ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
- USB_REQ_GET_STATUS, USB_DIR_IN | type, 0, target, status,
- sizeof(*status), USB_CTRL_GET_TIMEOUT);
+ USB_REQ_GET_STATUS, USB_DIR_IN | type, 0, target, &status,
+ sizeof(status), USB_CTRL_GET_TIMEOUT);
- *(u16 *)data = *status;
- kfree(status);
+ *(u16 *)data = status;
return ret;
}
-
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