linux-kernel - Re: [PATCH v3 05/15] bus: ts-nbus: use bitmap_get

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Message-ID: <37dc5907-b04f-4879-8271-68e36a6a2924@baylibre.com>
Date: Thu, 20 Feb 2025 11:16:44 -0600
From: David Lechner <dlechner@...libre.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>,
 Simon Horman <horms@...nel.org>
Cc: Linus Walleij <linus.walleij@...aro.org>,
 Bartosz Golaszewski <brgl@...ev.pl>, Andy Shevchenko <andy@...nel.org>,
 Geert Uytterhoeven <geert@...ux-m68k.org>,
 Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Ulf Hansson <ulf.hansson@...aro.org>,
 Peter Rosin <peda@...ntia.se>, Andrew Lunn <andrew@...n.ch>,
 Heiner Kallweit <hkallweit1@...il.com>, Russell King
 <linux@...linux.org.uk>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Vinod Koul <vkoul@...nel.org>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Nuno Sá
 <nuno.sa@...log.com>, Liam Girdwood <lgirdwood@...il.com>,
 Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
 Takashi Iwai <tiwai@...e.com>, linux-gpio@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
 linux-mmc@...r.kernel.org, netdev@...r.kernel.org,
 linux-phy@...ts.infradead.org, linux-sound@...r.kernel.org
Subject: Re: [PATCH v3 05/15] bus: ts-nbus: use bitmap_get_value8()

On 2/20/25 6:06 AM, Andy Shevchenko wrote:
> On Thu, Feb 20, 2025 at 12:17 PM Simon Horman <horms@...nel.org> wrote:
>> On Mon, Feb 10, 2025 at 04:33:31PM -0600, David Lechner wrote:
> 
> ...
> 
>> But when compiling with GCC 14.2.0 I see warnings that values
>> is used uninitialised - bitmap_set_value8() appears to rely on
>> it being so.
> 
>> In file included from drivers/bus/ts-nbus.c:13:
>> In function ‘bitmap_write’,
>>     inlined from ‘ts_nbus_reset_bus’ at drivers/bus/ts-nbus.c:111:2:
>> ./include/linux/bitmap.h:818:12: error: ‘values’ is used uninitialized [-Werror=uninitialized]
>>   818 |         map[index] &= (fit ? (~(mask << offset)) : ~BITMAP_FIRST_WORD_MASK(start));
>>       |         ~~~^~~~~~~
> 
> Heh, the compiler is dumb. Even if it's not initialised we do not care.
> 
> ...
> 
> Wondering if the bitmap_write() will work better...
> 

It is already using that:

#define bitmap_set_value8(map, value, start)		\
	bitmap_write(map, value, start, BITS_PER_BYTE)