Hi, Nathan Chancellor <natechancellor@xxxxxxxxx> writes: > On Mon, Feb 24, 2020 at 01:42:57PM -0800, Nick Desaulniers wrote: >> On Thu, Feb 20, 2020 at 8:57 PM Nathan Chancellor >> <natechancellor@xxxxxxxxx> 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? > > $ sed -n 537,555p drivers/usb/gadget/udc/bdc/bdc_ep.c > /* callback to gadget layer when xfr completes */ > static void bdc_req_complete(struct bdc_ep *ep, struct bdc_req *req, > int status) > { > struct bdc *bdc = ep->bdc; > > if (req == NULL || &req->queue == NULL || &req->usb_req == NULL) > return; > > dev_dbg(bdc->dev, "%s ep:%s status:%d\n", __func__, ep->name, status); > list_del(&req->queue); > req->usb_req.status = status; > usb_gadget_unmap_request(&bdc->gadget, &req->usb_req, ep->dir); > if (req->usb_req.complete) { > spin_unlock(&bdc->lock); > usb_gadget_giveback_request(&ep->usb_ep, &req->usb_req); > spin_lock(&bdc->lock); > } > } > > It looks like req->usb_req.complete is checked before being passed to > usb_gadget_giveback_request. So the patch as it stands is correct, > unless those checks needed to be something else. > > Felipe, could you clarify or pick up this patch if it is correct? This > is one of two warnings that I see for -Wtautological-compare and I want > it turned on for 5.7 and it'd be nice to be warning free, especially > since I sent this patch back in October :/ hmm, I don't have that patch in my inbox. Could you resend it? -- balbi
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