Am Montag, 3. Dezember 2012, 17:34:07 schrieb Stefan Hajnoczi:
> On Mon, Dec 3, 2012 at 2:20 PM, Laurent Navet <laurent.navet@xxxxxxxxx>
wrote:
> > staging: line6: driver.c
> >
> > The semantic patch that makes this output is available
> > in scripts/coccinelle/api/memdup.cocci.
> >
> > Signed-off-by: Laurent Navet <laurent.navet@xxxxxxxxx>
> > ---
> >
> > drivers/staging/line6/driver.c | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/staging/line6/driver.c
> > b/drivers/staging/line6/driver.c index f5c19b2..e1d6241 100644
> > --- a/drivers/staging/line6/driver.c
> > +++ b/drivers/staging/line6/driver.c
> > @@ -331,14 +331,13 @@ int line6_version_request_async(struct usb_line6
> > *line6)>
> > char *buffer;
> > int retval;
> >
> > - buffer = kmalloc(sizeof(line6_request_version), GFP_ATOMIC);
> > + buffer = kmemdup(line6_request_version,
> > + sizeof(line6_request_version), GFP_ATOMIC);
> >
> > if (buffer == NULL) {
> >
> > dev_err(line6->ifcdev, "Out of memory");
> > return -ENOMEM;
> >
> > }
> >
> > - memcpy(buffer, line6_request_version,
> > sizeof(line6_request_version)); -
> >
> > retval = line6_send_raw_message_async(line6, buffer,
> >
> > sizeof(line6_request_version
> > ));
> >
> > kfree(buffer);
> >
> > --
> > 1.7.10.4
>
> Your change is fine but I'm not sure whether we should allocate memory
> in the first place:
I can't remember the precise reason for this copy operation, it was related to
which type of memory is allowed for a URB data block, and memory declared with
"static const char[]" at global scope in the driver is not allowed. I just
verified on my system (kernel 3.4.11) that requesting the device's firmware
version doesn't work when passing the line6_request_version pointer directly
(instead of its kmemdup copy), so I think the kmemdup is necessary here. It's
a bit unsatisfactory to make a copy just because the original data is not
accessible for whatever reason, but I don't know of a better solution. Maybe
somebody else can clarify this or propose an alternative method?
Kind regards,
Markus
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