From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>,
Petr Mladek <pmladek@suse.com>,
linux-media@vger.kernel.org,
Dave Stevenson <dave.stevenson@raspberrypi.com>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
laurent.pinchart@ideasonboard.com, mchehab@kernel.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 1/1] lib/vsprintf: Add support for printing V4L2 and DRM fourccs
Date: Wed, 1 Apr 2020 18:13:32 +0300 [thread overview]
Message-ID: <20200401151332.GU1922688@smile.fi.intel.com> (raw)
In-Reply-To: <080ddddf-717e-61dc-8522-fbdbe52da94a@xs4all.nl>
On Wed, Apr 01, 2020 at 04:13:51PM +0200, Hans Verkuil wrote:
> On 4/1/20 4:05 PM, Sakari Ailus wrote:
> > Add a printk modifier %ppf (for pixel format) for printing V4L2 and DRM
> > pixel formats denoted by 4ccs. The 4cc encoding is the same for both so
> > the same implementation can be used.
%p4cc ?
> > + char ch[2] = { 0 };
>
> This can just be '{ };'
The latter is GCC extension, while above is C standard. Former is slightly
better I think. Though see below.
> > + unsigned int i;
> > +
> > + if (check_pointer(&buf, end, fourcc, spec))
> > + return buf;
> > +
> > + switch (fmt[1]) {
> > + case 'f':
> > + for (i = 0; i < sizeof(*fourcc); i++) {
> > + ch[0] = *fourcc >> (i << 3);
>
> You need to AND with 0x7f, otherwise a big endian fourcc (bit 31 is set)
> will look wrong. Also, each character is standard 7 bit ascii, bit 7 isn't
> used except to indicate a BE variant.
Why not to do it once by a flag and do reset it once?
u32 tmp = *fourcc;
bool be4cc = tmp & BIT(31);
tmp &= BIT(31);
On top of that, as promised above, why not simple do it in a simpler way, i.e.
using standard idiom:
for (i = 0; i < sizeof(*fourcc); i++) {
if (buf < end)
*buf = tmp >> (i * 8);
buf++;
}
?
> > + buf = string(buf, end, ch, spec);
> > + }
> > +
> > + if (*fourcc & BIT(31))
> > + buf = string(buf, end, "-BE", spec);
Another possibility
u8 ch[8];
if (*fourcc & BIT(31)) {
put_unaligned_be32(tmp, &ch[0]);
strcpy(&ch[4], "-BE");
} else {
put_unaligned_le32(tmp, &ch[0]);
strcpy(&ch[4], "-LE");
}
return string(buf, end, &ch[0], spec);
> > + return buf;
> > + default:
> > + return error_string(buf, end, "(%pp?)", spec);
> > + }
> > +}
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2020-04-01 15:13 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-01 14:05 [PATCH 1/1] lib/vsprintf: Add support for printing V4L2 and DRM fourccs Sakari Ailus
2020-04-01 14:13 ` Hans Verkuil
2020-04-01 15:13 ` Andy Shevchenko [this message]
2020-04-02 7:32 ` Sakari Ailus
2020-04-06 7:37 ` Pekka Paalanen
2020-04-02 7:18 ` Sakari Ailus
2020-04-02 8:34 ` Jani Nikula
2020-04-02 8:52 ` Sakari Ailus
2020-04-02 13:53 ` Mauro Carvalho Chehab
2020-04-02 23:28 ` Joe Perches
2020-04-02 23:26 ` Joe Perches
2020-04-03 6:37 ` Jani Nikula
2020-04-03 13:11 ` Joe Perches
2020-04-27 14:50 Sakari Ailus
2020-04-27 14:54 ` Sakari Ailus
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200401151332.GU1922688@smile.fi.intel.com \
--to=andriy.shevchenko@linux.intel.com \
--cc=dave.stevenson@raspberrypi.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=hverkuil@xs4all.nl \
--cc=laurent.pinchart@ideasonboard.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=mchehab@kernel.org \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=sakari.ailus@linux.intel.com \
--cc=sergey.senozhatsky@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).