linux-kernel - Re: [PATCH v2 1/1] iio: adc: qcom-spmi-adc5: Fix the channel name

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Y8gCRECOja+FxRsf@smile.fi.intel.com>
Date:   Wed, 18 Jan 2023 16:29:24 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Nuno Sá <nuno.sa@...log.com>,
        linux-arm-msm@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH v2 1/1] iio: adc: qcom-spmi-adc5: Fix the channel name

On Wed, Jan 18, 2023 at 03:04:23PM +0100, Marijn Suijten wrote:
> On 2023-01-18 15:22:42, Andy Shevchenko wrote:

...

> > > > +	name = devm_kasprintf(dev, GFP_KERNEL, "%pfwP", fwnode);
> > > 
> > > Is this better/cleaner than copying the string from fwnode_get_name?
> > 
> > Coying to where? And what would be the lifetime of that string?
> > 
> > With devm_kasprintf():
> > - we don't care how long the string is
> > - we don't care about corner cases of lifetime as it's the same as
> >   device itself (i.o.w. the same as the IIO device container)
> 
> Curious if there isn't a devm_strdup(name) or similar?  Main point is
> that %pfwP seems like magic when fwnode_get_name is not (but returns a
> const string that we cannot modify).

The devm_kstrdup(fwnode_get_name()) is an open coded variant of the above.
I don't think we need to open code and produce NIH even a single API. And
no, there is no magic behind that. At least from the fwnode point of view.

You may very well say that > 1500 instances of "%pOF" is a magic...

> If there is not, let's stick with
> devm_kasprintf().

There is, but I'm against it. See above why.

> > > > +	name[strchrnul(name, '@') - name] = '\0';
> > > 
> > > This is the same as *strchrnul(name, '@') = '\0'; if I'm not mistaken.
> > 
> > Yes, But it's harder to read and understand. I believe the compiler has
> > enough power to optimize this to the same assembly code.
> 
> I find the latter clearer as it doesn't require the reader to figure out
> that name - name cancels itself out.  Alternatively we can write
> strchrnul(name, '@')[0].

I don't like to have Pythonisms in the C code, really.

P.S. I guess this little patch already emptied my bandwidth, so I leave
any further discussion to you and IIO maintainers. Thank you for the
review!

-- 
With Best Regards,
Andy Shevchenko