Re: Printing bitfields in the kernel (Re: [PATCH] drm: Parse Colorimetry data block from EDID)

From: Joe Perches <joe@perches.com>
To: Pekka Paalanen <ppaalanen@gmail.com>,
	Algea Cao <algea.cao@rock-chips.com>
Cc: mripard@kernel.org, tzimmermann@suse.de,
	linux-kernel@vger.kernel.org, airlied@linux.ie,
	dri-devel@lists.freedesktop.org,
	maarten.lankhorst@linux.intel.com, daniel@ffwll.ch,
	linux-rockchip@lists.infradead.org
Subject: Re: Printing bitfields in the kernel (Re: [PATCH] drm: Parse Colorimetry data block from EDID)
Date: Thu, 27 Aug 2020 21:58:22 -0700	[thread overview]
Message-ID: <1fd895d12c756478ebfb92de1252b772b6fd417a.camel@perches.com> (raw)
In-Reply-To: <20200827103456.57edaf59@eldfell>

On Thu, 2020-08-27 at 10:34 +0300, Pekka Paalanen wrote:
> On Wed, 26 Aug 2020 22:23:28 +0800
> Algea Cao <algea.cao@rock-chips.com> wrote:
> 
> > CEA 861.3 spec adds colorimetry data block for HDMI.
> > Parsing the block to get the colorimetry data from
> > panel.

If flags are int, I could imagine another %p<foo> extension
where %*p<foo> is used like:

	printk("flags: %*p<foo>n", flags, bitstrings)

where flags is:

	BIT(0)
	BIT(1)
	...
	BIT(last)

and

	char *bitstrings[] = {
		"bit 0 description",
		"bit 1 description",
		...
		"last bit description"
	};

Or define YA struct with 2 entries as the struct members
and use that.

struct foo {
	unsigned long flags,
	char ** descriptions,
};

	struct foo bar = {.flags = <flags> .descriptions = bitstrings};

	printk("flags: %p<foo>\n, &bar);