linux-kernel - Re: [PATCH 1/1] lib: devres: Add error information printing for __devm_ioremap

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Message-ID: <CAMuHMdWeJkDvhf-J-S4dLqKmSvqnkf+AcWdjyPNu-G8zu2jOkA@mail.gmail.com>
Date:   Mon, 7 Jun 2021 10:15:15 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH 1/1] lib: devres: Add error information printing for __devm_ioremap_resource()

Hi Leizhen,

On Mon, Jun 7, 2021 at 9:11 AM Leizhen (ThunderTown)
<thunder.leizhen@...wei.com> wrote:
> On 2021/5/17 15:04, Geert Uytterhoeven wrote:
> > On Wed, Apr 28, 2021 at 8:33 AM Zhen Lei <thunder.leizhen@...wei.com> wrote:
> >> Ensure that all error handling branches print error information. In this
> >> way, when this function fails, the upper-layer functions can directly
> >> return an error code without missing debugging information. Otherwise,
> >> the error message will be printed redundantly or missing.
> >>
> >> Fixes: 35bd8c07db2c ("devres: keep both device name and resource name in pretty name")
> >> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> >
> > Thanks for your patch, which is now commit 5c3e241f5246445d ("lib:
> > devres: Add error information printing for __devm_ioremap_resource()")
> > in driver-core-next.
> >
> >> --- a/lib/devres.c
> >> +++ b/lib/devres.c
> >> @@ -157,8 +157,10 @@ __devm_ioremap_resource(struct device *dev, const struct resource *res,
> >>                                              dev_name(dev), res->name);
> >>         else
> >>                 pretty_name = devm_kstrdup(dev, dev_name(dev), GFP_KERNEL);
> >> -       if (!pretty_name)
> >> +       if (!pretty_name) {
> >> +               dev_err(dev, "can't generate pretty name for resource %pR\n", res);
> >
> > If the above fails, it is due to a memory allocation failure, and the
> > memory allocation core will have already printed an error message.
> > So there is no need to print a second message.
> > Hence IMHO this commit should be reverted.
>
> If the memory allocation fails, only the 'size' is printed, but the start address of
> the 'res' is not printed. So the printing here is not repeated. The start address is
> the more critical help information.

Does that actually matter?
What can the user or developer do to fix this problem, with the
additional knowledge of the resource's start address?

> >>                 return IOMEM_ERR_PTR(-ENOMEM);
> >> +       }
> >>
> >>         if (!devm_request_mem_region(dev, res->start, size, pretty_name)) {
> >>                 dev_err(dev, "can't request region for resource %pR\n", res);

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds