linux-kernel - Re: [PATCH net-next v7 1/6] net: marvell: prestera: Add driver for Prestera family ASIC devices

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Message-ID: <CAHp75VdyahsNyOK9_7mFGHFg_O47jVQWro-mhU0n=1K17Eeg8Q@mail.gmail.com>
Date:   Tue, 8 Sep 2020 12:38:04 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Vadym Kochan <vadym.kochan@...ision.eu>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jiri Pirko <jiri@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>,
        Andrew Lunn <andrew@...n.ch>,
        Oleksandr Mazur <oleksandr.mazur@...ision.eu>,
        Serhiy Boiko <serhiy.boiko@...ision.eu>,
        Serhiy Pshyk <serhiy.pshyk@...ision.eu>,
        Volodymyr Mytnyk <volodymyr.mytnyk@...ision.eu>,
        Taras Chornyi <taras.chornyi@...ision.eu>,
        Andrii Savka <andrii.savka@...ision.eu>,
        netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mickey Rachamim <mickeyr@...vell.com>
Subject: Re: [PATCH net-next v7 1/6] net: marvell: prestera: Add driver for
 Prestera family ASIC devices

On Tue, Sep 8, 2020 at 11:35 AM Vadym Kochan <vadym.kochan@...ision.eu> wrote:
> On Fri, Sep 04, 2020 at 10:12:07PM +0300, Andy Shevchenko wrote:
> > On Fri, Sep 4, 2020 at 7:52 PM Vadym Kochan <vadym.kochan@...ision.eu> wrote:

...

> > > +       words[3] |= FIELD_PREP(PRESTERA_W3_HW_DEV_NUM, (dsa->hw_dev_num >> 5));
> >
> > Ditto.
> >
> I am not sure 5 needs to be defined as macro as it just moves
> hw_dev_num's higher bits into the last word.

And why 5? I want 6, for example!

...

> > > +       err = prestera_switch_init(sw);
> > > +       if (err) {
> > > +               kfree(sw);
> >
> > > +               return err;
> > > +       }
> > > +
> > > +       return 0;
> >
> > return err;
> >
> why not keep 'return 0' as indication of success point ?

Simple longer, but I'm not insisting. Your choice.

...

> > > +                       if (b == 0)
> > > +                               continue;
> > > +
> > > +                       prestera_sdma_rx_desc_set_next(sdma,
> > > +                                                      ring->bufs[b - 1].desc,
> > > +                                                      buf->desc_dma);
> > > +
> > > +                       if (b == PRESTERA_SDMA_RX_DESC_PER_Q - 1)
> > > +                               prestera_sdma_rx_desc_set_next(sdma, buf->desc,
> > > +                                                              head->desc_dma);
> >
> > I guess knowing what the allowed range of bnum the above can be optimized.
> >
> You mean to replace PRESTERA_SDMA_RX_DESC_PER_Q by bnum ?

I don't know what you meant in above. It might be a bug, it might be
that bnum is redundant and this definition may be used everywhere...
But I believe there is room for improvement when I see pattern like

  for (i < X) {
    ...
    if (i == 0) {
      ...
    } else if (i == X - 1) {
      ...
    }
  }

Either it can be while-loop (or do-while) with better semantics for
the first and last item to handle or something else.
Example from another review [1] in case you wonder how changes can be
made. Just think about it.

[1]: https://www.spinics.net/lists/linux-pci/msg60826.html (before)
https://www.spinics.net/lists/linux-pci/msg62043.html (after)

-- 
With Best Regards,
Andy Shevchenko