linux-kernel - Re: [PATCH] io: Fix return type of _inb and

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Message-ID: <CAK8P3a37s8ct5moydwwVO+C5TLfW+GU6VS-+zuAQfZzs2czXaw@mail.gmail.com>
Date:   Mon, 27 Jul 2020 10:41:30 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     John Garry <john.garry@...wei.com>
Cc:     Stafford Horne <shorne@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Wei Xu <xuwei5@...ilicon.com>,
        Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] io: Fix return type of _inb and _inl

On Mon, Jul 27, 2020 at 10:30 AM John Garry <john.garry@...wei.com> wrote:
> On 27/07/2020 09:04, Arnd Bergmann wrote:> On Sun, Jul 26, 2020 at 2:53
> PM Stafford Horne <shorne@...il.com> wrote:
> >>
> >> On Sun, Jul 26, 2020 at 12:00:37PM +0300, Andy Shevchenko wrote:
> >>> On Sun, Jul 26, 2020 at 6:14 AM Stafford Horne <shorne@...il.com> wrote:
> >>>>
> >>>> The return type of functions _inb, _inw and _inl are all u16 which looks
> >>>> wrong.  This patch makes them u8, u16 and u32 respectively.
> >>>>
> >>>> The original commit text for these does not indicate that these should
> >>>> be all forced to u16.
> >>>
> >>> Is it in alight with all architectures? that support this interface natively?
> >>>
> >>> (Return value is arch-dependent AFAIU, so it might actually return
> >>> 16-bit for byte read, but I agree that this is weird for 32-bit value.
> >>> I think you have elaborate more in the commit message)
> >>
> >> Well, this is the generic io code,  at least these api's appear to not be different
> >> for each architecture.  The output read by the architecture dependant code i.e.
> >> __raw_readb() below is getting is placed into a u8.  So I think the output of
> >> the function will be u8.
> >>
> >> static inline u8 _inb(unsigned long addr)
> >> {
> >>          u8 val;
> >>
> >>          __io_pbr();
> >>          val = __raw_readb(PCI_IOBASE + addr);
> >>          __io_par(val);
> >>          return val;
> >> }
> >>
> >> I can expand the commit text, but I would like to get some comments from the
> >> original author to confirm if this is an issue.
> >
> > I think your original version is fine, this was clearly just a typo and I've
> > applied your fix now and will forward it to Linus in the next few days,
> > giving John the chance to add his Ack or further comments.
> >
> > Thanks a lot for spotting it and sending a fix.
>
> Thanks Arnd.
>
> Yeah, these looks like copy+paste errors on my part:
>
> Reviewed-by: John Garry <john.garry@...wei.com>

Thanks!

>
> I'll give this patch a spin, but not expecting any differences (since
> original seems ok).
>
> Note that kbuild robot also reported this:
> https://lore.kernel.org/lkml/202007140549.J7X9BVPT%25lkp@intel.com/
>
> Extract:
>
> include/asm-generic/io.h:521:22: sparse: sparse: incorrect type in
> argument 1 (different base types) @@     expected unsigned int
> [usertype] value @@     got restricted __le32 [usertype] @@
>     include/asm-generic/io.h:521:22: sparse:     expected unsigned int
> [usertype] value
>     include/asm-generic/io.h:521:22: sparse:     got restricted __le32
> [usertype]
>
> But they look like issues which were in the existing code.

Yes, this driver code (atm/ambassador.c) seems to have been broken that
way since it was merged in 1999.

      Arnd