Re: [PATCH v3 1/4] auxdisplay: Add 7-segment LED display driver

From: Yury Norov <yury.norov@gmail.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Chris Packham <Chris.Packham@alliedtelesis.co.nz>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Andy Shevchenko <andy@kernel.org>,
	"geert@linux-m68k.org" <geert@linux-m68k.org>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>,
	"krzysztof.kozlowski+dt@linaro.org"
	<krzysztof.kozlowski+dt@linaro.org>,
	"conor+dt@kernel.org" <conor+dt@kernel.org>,
	"andrew@lunn.ch" <andrew@lunn.ch>,
	"gregory.clement@bootlin.com" <gregory.clement@bootlin.com>,
	"sebastian.hesselbarth@gmail.com"
	<sebastian.hesselbarth@gmail.com>, "pavel@ucw.cz" <pavel@ucw.cz>,
	"lee@kernel.org" <lee@kernel.org>,
	"linux-leds@vger.kernel.org" <linux-leds@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v3 1/4] auxdisplay: Add 7-segment LED display driver
Date: Sun, 3 Mar 2024 12:56:21 -0800	[thread overview]
Message-ID: <ZeTj9cRkafeps0dT@yury-ThinkPad> (raw)
In-Reply-To: <CAHp75VfCt-3wOKykUNE8MnV9nHKvkbDY9vs25j559+cX-OudzQ@mail.gmail.com>

On Sun, Mar 03, 2024 at 10:35:03PM +0200, Andy Shevchenko wrote:
> +Cc: Rasmus, Yury
> 
> On Sun, Mar 3, 2024 at 9:58 PM Chris Packham
> <Chris.Packham@alliedtelesis.co.nz> wrote:
> > On 2/03/24 07:18, Andy Shevchenko wrote:
> 
> ...
> 
> > >> +    DECLARE_BITMAP(values, 8);
> > >> +    bitmap_zero(values, 8);
> > > Why do you need this zeroing?
> > >
> > >> +    bitmap_set_value8(values, map_to_seg7(&map->map.seg7, linedisp->buf[0]), 0);
> 
> > Without the zeroing above GCC complains about use  of a potentially
> > uninitialized variable here. I think because bitmap_set_value8() does &=
> > and |=.
> 
> Hmm... Rasmus, Yury, do we have any ideas how to get rid of this redundancy?

DECLARE_BITMAP(values, 8) = { 0 };