lkml.org 
[lkml]   [2020]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
SubjectRe: [PATCH] usb: gadget: udc: bdc: Remove unnecessary NULL checks in bdc_req_complete
On Thu, Feb 20, 2020 at 8:57 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> I know it has been a while but ping?

Sorry! Too many bugs...barely treading water! Send help!

>
> On Tue, Oct 22, 2019 at 05:20:15PM -0700, Nathan Chancellor wrote:
> > When building with Clang + -Wtautological-pointer-compare:
> >
> > drivers/usb/gadget/udc/bdc/bdc_ep.c:543:28: warning: comparison of
> > address of 'req->queue' equal to a null pointer is always false
> > [-Wtautological-pointer-compare]
> > if (req == NULL || &req->queue == NULL || &req->usb_req == NULL)
> > ~~~~~^~~~~ ~~~~
> > drivers/usb/gadget/udc/bdc/bdc_ep.c:543:51: warning: comparison of
> > address of 'req->usb_req' equal to a null pointer is always false
> > [-Wtautological-pointer-compare]
> > if (req == NULL || &req->queue == NULL || &req->usb_req == NULL)
> > ~~~~~^~~~~~~ ~~~~
> > 2 warnings generated.
> >
> > As it notes, these statements will always evaluate to false so remove
> > them.

`req` is an instance of a `struct bdc_req` defined in
drivers/usb/gadget/udc/bdc/bdc.h as:
333 struct bdc_req {
334 struct usb_request usb_req;
335 struct list_head queue;
336 struct bdc_ep *ep;
337 /* only one Transfer per request */
338 struct bd_transfer bd_xfr;
339 int epnum;
340 };

So indeed the non-pointer, struct members can never be NULL.

I think the second check that was removed should be
`req->usb_req.complete == NULL`, since otherwise `&req->usb_req` may
be passed to usb_gadget_giveback_request which tries to invoke the
`complete` member as a callback. There are numerous places in
drivers/usb/gadget/udc/bdc/bdc_ep.c that assign `complete = NULL`.

Can the maintainers clarify?

> >
> > Fixes: efed421a94e6 ("usb: gadget: Add UDC driver for Broadcom USB3.0 device controller IP BDC")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/749
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > ---
> >
> > Note: I am not sure if these checks were intended to check if the
> > contents of these arrays were NULL or if there should be some other
> > checks in lieu of these; I am not familiar with the USB subsystem to
> > answer this but I will happily respin the patch if this is not correct.
> >
> > drivers/usb/gadget/udc/bdc/bdc_ep.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/gadget/udc/bdc/bdc_ep.c b/drivers/usb/gadget/udc/bdc/bdc_ep.c
> > index a4d9b5e1e50e..d49c6dc1082d 100644
> > --- a/drivers/usb/gadget/udc/bdc/bdc_ep.c
> > +++ b/drivers/usb/gadget/udc/bdc/bdc_ep.c
> > @@ -540,7 +540,7 @@ static void bdc_req_complete(struct bdc_ep *ep, struct bdc_req *req,
> > {
> > struct bdc *bdc = ep->bdc;
> >
> > - if (req == NULL || &req->queue == NULL || &req->usb_req == NULL)
> > + if (req == NULL)
> > return;
> >
> > dev_dbg(bdc->dev, "%s ep:%s status:%d\n", __func__, ep->name, status);
> > --
> > 2.23.0
> >
>
> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200221045740.GA43417%40ubuntu-m2-xlarge-x86.



--
Thanks,
~Nick Desaulniers

\
 
 \ /
  Last update: 2020-02-24 22:45    [W:0.086 / U:0.124 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site