linux-kernel - Re: [PATCH v19 2/9] usb: dwc3: core: Access XHCI address space temporarily to read port info

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Message-ID: <CAA8EJpr94_uCHoJyQd2uQyZ35xXixPPMHPVGXciZn+GftUUjnA@mail.gmail.com>
Date: Fri, 5 Apr 2024 23:36:41 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Bjorn Andersson <quic_bjorande@...cinc.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Johan Hovold <johan@...nel.org>, 
	Krishna Kurapati <quic_kriskura@...cinc.com>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Rob Herring <robh@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Wesley Cheng <quic_wcheng@...cinc.com>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Thinh Nguyen <Thinh.Nguyen@...opsys.com>, Felipe Balbi <balbi@...nel.org>, devicetree@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org, 
	linux-kernel@...r.kernel.org, quic_ppratap@...cinc.com, 
	quic_jackp@...cinc.com, Johan Hovold <johan+linaro@...nel.org>
Subject: Re: [PATCH v19 2/9] usb: dwc3: core: Access XHCI address space
 temporarily to read port info

On Fri, 5 Apr 2024 at 22:27, Bjorn Andersson <quic_bjorande@...cinc.com> wrote:
>
> On Fri, Apr 05, 2024 at 06:43:56AM +0200, Greg Kroah-Hartman wrote:
> > On Thu, Apr 04, 2024 at 06:25:48PM -0700, Bjorn Andersson wrote:
> > > On Thu, Apr 04, 2024 at 02:58:29PM +0200, Greg Kroah-Hartman wrote:
> > > > On Thu, Apr 04, 2024 at 10:07:27AM +0200, Krzysztof Kozlowski wrote:
> > > > > On 04/04/2024 09:21, Johan Hovold wrote:
> > > > > > On Thu, Apr 04, 2024 at 10:42:22AM +0530, Krishna Kurapati wrote:
> > > > > >
> > > > > >> +static int dwc3_get_num_ports(struct dwc3 *dwc)
> > > > > >> +{
> > > > > >> +    void __iomem *base;
> > > > > >> +    u8 major_revision;
> > > > > >> +    u32 offset;
> > > > > >> +    u32 val;
> > > > > >> +
> > > > > >> +    /*
> > > > > >> +     * Remap xHCI address space to access XHCI ext cap regs since it is
> > > > > >> +     * needed to get information on number of ports present.
> > > > > >> +     */
> > > > > >> +    base = ioremap(dwc->xhci_resources[0].start,
> > > > > >> +                   resource_size(&dwc->xhci_resources[0]));
> > > > > >> +    if (!base)
> > > > > >> +            return PTR_ERR(base);
> > > > > >
> > > > > > This is obviously still broken. You need to update the return value as
> > > > > > well.
> > > > > >
> > > > > > Fix in v20.
> > > > >
> > > > > If one patchset reaches 20 versions, I think it is time to stop and
> > > > > really think from the beginning, why issues keep appearing and reviewers
> > > > > are still not happy.
> > > > >
> > > > > Maybe you did not perform extensive internal review, which you are
> > > > > encouraged to by your own internal policies, AFAIR. Before posting next
> > > > > version, please really get some internal review first.
> > > >
> > > > Also get those internal reviewers to sign-off on the commits and have
> > > > that show up when you post them next.  That way they are also
> > > > responsible for this patchset, it's not fair that they are making you do
> > > > all the work here :)
> > > >
> > >
> > > I like this idea and I'm open to us changing our way of handling this.
> > >
> > > But unless such internal review brings significant input to the
> > > development I'd say a s-o-b would take the credit from the actual
> > > author.
> >
> > It does not do that at all.  It provides proof that someone else has
> > reviewed it and agrees with it.  Think of it as a "path of blame" for
> > when things go bad (i.e. there is a bug in the submission.)  Putting
> > your name on it makes you take responsibility if that happens.
> >
>
> Right, this is why I like your idea.
>
> But as s-o-b either builds a trail of who handled the patch, or reflects
> that it was co-authored by multiple people, I don't think either one
> properly reflects reality.
>
> > > We've discussed a few times about carrying Reviewed-by et al from the
> > > internal reviews, but as maintainer I dislike this because I'd have no
> > > way to know if a r-b on vN means the patch was reviewed, or if it was
> > > just "accidentally" carried from v(N-1).
> > > But it might be worth this risk, is this something you think would be
> > > appropriate?
> >
> > For some companies we REQUIRE this to happen due to low-quality
> > submissions and waste of reviewer's time.  Based on the track record
> > here for some of these patchsets, hopefully it doesn't become a
> > requirement for this company as well :)
> >
>
> Interesting, I was under the impression that we (maintainers) didn't
> want such internally originating tags.

But why? It just means that the patch has been reviewed. In some rare
cases we explicitly ask a developer to have all the patches reviewed
before sending them upstream. In such a case having an R-B tag
fulfills the expectation of the maintainer: it shows that another
engineer has reviewed the patch.

> If that's not the case, then I'd be happy to adjust our internal
> guidelines.

-- 
With best wishes
Dmitry