linux-kernel - Re: [PATCH v3 1/2] vsprintf: Add %p[mM]U for uppercase MAC address

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Message-ID: <2023042842-embattled-collected-8638@gregkh>
Date:   Fri, 28 Apr 2023 09:19:19 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Konrad Gräfe <k.graefe@...eware.de>,
        Quentin Schulz <quentin.schulz@...obroma-systems.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Andrzej Pietrasiewicz <andrzej.p@...labora.com>,
        Felipe Balbi <balbi@...com>, stable@...r.kernel.org
Subject: Re: [PATCH v3 1/2] vsprintf: Add %p[mM]U for uppercase MAC address

On Fri, Apr 28, 2023 at 08:56:59AM +0200, Rasmus Villemoes wrote:
> On 27/04/2023 13.51, Konrad Gräfe wrote:
> > The CDC-ECM specification requires an USB gadget to send the host MAC
> > address as uppercase hex string. This change adds the appropriate
> > modifier.
> 
> Thinking more about it, I'm not sure this is appropriate, not for a
> single user like this. vsprintf() should not and cannot satisfy all
> possible string formatting requirements for the whole kernel. The %pX
> extensions are convenient for use with printk() and friends where one
> needs what in other languages would be "string interpolation" (because
> then the caller doesn't need to deal with temporary stack buffers and
> pass them as %s arguments), but for single items like this, snprintf()
> is not necessarily the right tool for the job.

But sprintf() already creates mac address strings today, adding
yet-another-modifier makes it so that we don't have to hand-roll this
type of logic in the individual drivers that require it.

thanks,

greg k-h