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

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Date: Sun, 3 Mar 2024 12:56:21 -0800
From: Yury Norov <yury.norov@...il.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Chris Packham <Chris.Packham@...iedtelesis.co.nz>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Andy Shevchenko <andy@...nel.org>,
	"geert@...ux-m68k.org" <geert@...ux-m68k.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"krzysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>,
	"andrew@...n.ch" <andrew@...n.ch>,
	"gregory.clement@...tlin.com" <gregory.clement@...tlin.com>,
	"sebastian.hesselbarth@...il.com" <sebastian.hesselbarth@...il.com>,
	"pavel@....cz" <pavel@....cz>, "lee@...nel.org" <lee@...nel.org>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 1/4] auxdisplay: Add 7-segment LED display driver

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@...iedtelesis.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 };