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From: Eugene Syromiatnikov <esyr@redhat.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	Michael Williams <michael.williams@arm.com>,
	linux-kernel@vger.kernel.org,
	Chunyan Zhang <zhang.chunyan@linaro.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	"Dmitry V. Levin" <ldv@altlinux.org>,
	Pratik Patel <pratikp@codeaurora.org>,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] coresight: do not use the BIT() macro in the UAPI header
Date: Tue, 24 Mar 2020 13:13:06 +0100	[thread overview]
Message-ID: <20200324121306.GA5735@asgard.redhat.com> (raw)
In-Reply-To: <20200324101938.GA2220478@kroah.com>

On Tue, Mar 24, 2020 at 11:19:38AM +0100, Greg Kroah-Hartman wrote:
> On Tue, Mar 24, 2020 at 10:53:04AM +0100, Eugene Syromiatnikov wrote:
> > On Tue, Mar 24, 2020 at 07:28:53AM +0100, Greg Kroah-Hartman wrote:
> > > On Tue, Mar 24, 2020 at 05:22:13AM +0100, Eugene Syromiatnikov wrote:
> > > > The BIT() macro definition is not available for the UAPI headers
> > > > (moreover, it can be defined differently in the user space); replace
> > > > its usage with the _BITUL() macro that is defined in <linux/const.h>.
> > > 
> > > Why is somehow _BITUL() ok to use here instead?
> > 
> > It is provided in an UAPI header (include/uapi/linux/const.h)
> > and is appropriately prefixed with an underscore to avoid conflicts.
> 
> Because no one uses _ in their own macros?  :)

Well, it is a reserved prefix (ANSI C99, 4.1.2 "Standard headers": "All
other identifiers that begin with an underscore and either an upper-case
letter or another underscore are reserved"), so valid C files shouldn't
use them.

> Anyway, this is fine, but if it's really the way forward, I think a lot
> of files will end up being changed...

There are 5 cases for using BIT() in UAPI headers so far (rtc.h[1],
serio.h[2], psci.h[3], pkt_sched.h[4], coresight-stm.h), two of them were
conversions from the open-coded variant; the usage of _BITUL in pkt_sched.h
made me think that it is the better approach since people tend to use
BIT-like macro anyway, so, by increasing a number of cases it may raise
awareness of the UAPI specifics.

[1] https://lore.kernel.org/lkml/20200324041209.GA30727@asgard.redhat.com/
[2] https://lore.kernel.org/lkml/20200324041341.GA32335@asgard.redhat.com/
[3] https://lore.kernel.org/lkml/20200324041526.GA1978@asgard.redhat.com/
[4] https://lore.kernel.org/lkml/20200324041920.GA7068@asgard.redhat.com/

> 
> thanks,
> 
> greg k-h
> 


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  reply	other threads:[~2020-03-24 12:13 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24  4:22 [PATCH] coresight: do not use the BIT() macro in the UAPI header Eugene Syromiatnikov
2020-03-24  6:28 ` Greg Kroah-Hartman
2020-03-24  9:53   ` Eugene Syromiatnikov
2020-03-24 10:19     ` Greg Kroah-Hartman
2020-03-24 12:13       ` Eugene Syromiatnikov [this message]
2020-03-24 15:31 ` Mathieu Poirier
2020-03-26 14:10   ` Greg Kroah-Hartman

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