Re: [PATCH v2 2/3] usb: dwc3: gadget: Add support for snps,reserved-endpoints property

Thinh Nguyen
2025-02-13T01:16:41Z

On Wed, Feb 12, 2025, Andy Shevchenko wrote:
> On Wed, Feb 12, 2025 at 01:10:17AM +0000, Thinh Nguyen wrote:
> > On Mon, Feb 03, 2025, Andy Shevchenko wrote:
> > > The snps,reserved-endpoints property lists the reserved endpoints
> > > that shouldn't be used for normal transfers. Add support for that
> > > to the driver.
>
> > > While at it, make sure we don't crash by a sudden access to those
> > > endpoints in the gadget driver.
>
> ^^^ (1)
>
> ...
>
> > > /* Reset resource allocation flags */
> > > - for (i = resource_index; i < dwc->num_eps && dwc->eps[i]; i++)
> > > - dwc->eps[i]->flags &= ~DWC3_EP_RESOURCE_ALLOCATED;
> > > + for (i = resource_index; i < dwc->num_eps; i++) {
> > > + dep = dwc->eps[i];
> > > + if (!dep)
> > > + continue;
> > > +
> > > + dep->flags &= ~DWC3_EP_RESOURCE_ALLOCATED;
> > > + }
> >
> > Please keep code refactoring as a separate patch.
>
> It's induced by the change you asked for, it's not a simple refactoring.
>
> Or do you want me to have the patch to check eps against NULL to be separated
> from this one (see (1) above)?

The condition "i < dwc->num && dwc->eps[i]" already does the NULL check.
The change here only move things around.

>
> > >
> > > return 0;
>
> ...
>
> > > +static int dwc3_gadget_parse_reserved_endpoints(struct dwc3 *dwc, const char *propname,
> > > + u8 *eps, u8 num)
> > > +{
> > > + u8 count;
> > > + int ret;
> > > +
> > > + if (!device_property_present(dwc->dev, propname))
> > > + return 0;
> > > +
> > > + ret = device_property_count_u8(dwc->dev, propname);
> > > + if (ret < 0)
> > > + return ret;
> > > + count = ret;
> > > +
> > > + ret = device_property_read_u8_array(dwc->dev, propname, eps, min(num, count));
> >
> > Why do min(num, count)? Can we just put the size of the eps array as
> > specified by the function doc.
>
> No, we can't ask more than there is. The call will fail in such a case.
> In case you wonder, the similar OF call also behaves in the same way.

Yeah, I realized that right after I wrote the comment and responded
after.

BR,
Thinh