linux-kernel - Re: [PATCH v7 1/3] lib/vsprintf: Add support for printing V4L2 and DRM fourccs

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Date:   Mon, 15 Feb 2021 17:54:47 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        Petr Mladek <pmladek@...e.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        dri-devel@...ts.freedesktop.org, hverkuil@...all.nl,
        laurent.pinchart@...asonboard.com, mchehab@...nel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joe Perches <joe@...ches.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH v7 1/3] lib/vsprintf: Add support for printing V4L2 and
 DRM fourccs

On Mon, Feb 15, 2021 at 03:56:50PM +0200, Sakari Ailus wrote:
> On Mon, Feb 15, 2021 at 03:31:29PM +0200, Andy Shevchenko wrote:
> > On Mon, Feb 15, 2021 at 01:40:28PM +0200, Sakari Ailus wrote:
> > > Add a printk modifier %p4cc (for pixel format) for printing V4L2 and DRM
> > > pixel formats denoted by fourccs. The fourcc encoding is the same for both
> > > so the same implementation can be used.
> > 
> > This version I almost like, feel free to add
> > Reviewed-by: From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > after considering addressing below nit-picks.

> > > +Examples::
> > > +
> > > +	%p4cc	BG12 little-endian (0x32314742)
> > 
> > No examples with spaces / non-printable / non-ascii characters
> 
> I can sure add an example that has a space. But do you think I really
> should add an example where invalid information is being printed?

I think you have to provide better coverage of what user can get out of this.
Perhaps one example with space and non-printable character is enough.

> > > +	char output[sizeof("1234 little-endian (0x01234567)")];
> > 
> > 1234 -> ABCD ? (Or XY12 to be closer to the reality)
> 
> I count in numbers... albeit the hexadecimal number there starts from zero.
> 
> I guess both would work though.
> 
> 0123 would be consistent.

Since letters can be printed the above is confusing a bit. I think XY12 is
closer to the reality than 0123.

-- 
With Best Regards,
Andy Shevchenko