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 19:21:03 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        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

Hi Petr,

On Mon, Feb 15, 2021 at 05:51:40PM +0100, Petr Mladek wrote:
> On Mon 2021-02-15 17:54:47, Andy Shevchenko wrote:
> > 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.
> 
> Ailus, are you going to send v8 with the two small changes? I mean a
> selftest with the space and the above sample code.

Yes, and a few more examples.

> 
> Anyway, feel free to add:
> 
> Reviewed-by: Petr Mladek <pmladek@...e.com>

Thank you.

It'd be great if we could merge this through the printk tree. Acks are
needed from the DRM people first.

-- 
Regards,

Sakari Ailus