From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
To: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
Cc: Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>,
Greg Kroah-Hartman
<gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>,
akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports
Date: Fri, 09 May 2014 14:20:45 -0700 [thread overview]
Message-ID: <536D46AD.3070608@zytor.com> (raw)
In-Reply-To: <4366326.1D6xUnlac7@wuerfel>
On 05/09/2014 02:12 PM, Arnd Bergmann wrote:
>
>> However, if we're going to have these devices I'm wondering if having
>> /dev/portw and /dev/portl (or something like that) might not make sense,
>> rather than requiring a system call per transaction.
>
> Actually the behavior of /dev/port for >1 byte writes seems questionable
> already: There are very few devices on which writing to consecutive
> port numbers makes sense. Normally you just want to write a series
> of bytes (or 16/32 bit words) into the same port number instead,
> as the outsb()/outsw()/outsl() functions do.
>
Indeed. I missed the detail that it increments the port index; it is
virtually guaranteed to be bogus.
-hpa
WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa@zytor.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Josh Triplett <josh@joshtriplett.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org
Subject: Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports
Date: Fri, 09 May 2014 14:20:45 -0700 [thread overview]
Message-ID: <536D46AD.3070608@zytor.com> (raw)
In-Reply-To: <4366326.1D6xUnlac7@wuerfel>
On 05/09/2014 02:12 PM, Arnd Bergmann wrote:
>
>> However, if we're going to have these devices I'm wondering if having
>> /dev/portw and /dev/portl (or something like that) might not make sense,
>> rather than requiring a system call per transaction.
>
> Actually the behavior of /dev/port for >1 byte writes seems questionable
> already: There are very few devices on which writing to consecutive
> port numbers makes sense. Normally you just want to write a series
> of bytes (or 16/32 bit words) into the same port number instead,
> as the outsb()/outsw()/outsl() functions do.
>
Indeed. I missed the detail that it increments the port index; it is
virtually guaranteed to be bogus.
-hpa
next prev parent reply other threads:[~2014-05-09 21:20 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-09 19:19 [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports Josh Triplett
2014-05-09 19:19 ` Josh Triplett
2014-05-09 19:21 ` [PATCH] mem.4, ioports.4: Document /dev/ioports Josh Triplett
2014-05-09 19:21 ` Josh Triplett
2014-05-13 8:27 ` Michael Kerrisk (man-pages)
2014-05-09 19:58 ` [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports Arnd Bergmann
2014-05-09 19:58 ` Arnd Bergmann
2014-05-09 20:54 ` H. Peter Anvin
2014-05-09 20:54 ` H. Peter Anvin
2014-05-09 21:12 ` Arnd Bergmann
2014-05-09 21:20 ` H. Peter Anvin [this message]
2014-05-09 21:20 ` H. Peter Anvin
[not found] ` <536D46AD.3070608-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2014-05-09 22:38 ` Josh Triplett
2014-05-09 22:38 ` Josh Triplett
2014-05-13 22:10 ` H. Peter Anvin
[not found] ` <53729873.2030805-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2014-05-15 21:56 ` josh-iaAMLnmF4UmaiuxdJuQwMA
2014-05-15 21:56 ` josh
2014-05-19 12:36 ` Arnd Bergmann
2014-05-19 12:36 ` Arnd Bergmann
2014-05-28 21:41 ` H. Peter Anvin
2014-05-28 21:41 ` H. Peter Anvin
[not found] ` <53865820.7010309-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2014-05-29 9:26 ` Arnd Bergmann
2014-05-29 9:26 ` Arnd Bergmann
2014-05-29 13:38 ` H. Peter Anvin
2014-05-29 13:38 ` H. Peter Anvin
[not found] ` <5387385B.1030203-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2014-05-30 11:32 ` Arnd Bergmann
2014-05-30 11:32 ` Arnd Bergmann
2015-12-22 10:52 ` Santosh Shukla
2015-12-22 10:52 ` Santosh Shukla
[not found] ` <CA+iXiiN8xFaiz6DwyLfWRFZ81pJZf=Fv1E60VZC-iSNPswaGEQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-12-22 21:56 ` Arnd Bergmann
2015-12-22 21:56 ` Arnd Bergmann
2015-12-22 22:02 ` H. Peter Anvin
[not found] ` <1592CC7D-B2F2-4E8B-BB90-4A20682B1FEE-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2015-12-22 22:11 ` Arnd Bergmann
2015-12-22 22:11 ` Arnd Bergmann
2015-12-23 11:34 ` Santosh Shukla
[not found] ` <CA+iXiiOsbC0MBaRwc5JgaTVRpdxHub5t2T=LrGaVN1AjKpiJgA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-12-29 13:28 ` Arnd Bergmann
2015-12-29 13:28 ` Arnd Bergmann
2015-12-29 15:53 ` Santosh Shukla
2015-12-29 15:53 ` Santosh Shukla
[not found] ` <CA+iXiiNKiMz=9BJgu3g=LggXjTv61Uwu+ibNfKeih3rK328LSQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-12-29 15:55 ` Santosh Shukla
2015-12-29 15:55 ` Santosh Shukla
[not found] ` <CA+iXiiM+TrciHROfgTcN01mfGEYuUCvpNRU0Qqgrt56VdCcR8Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-12-29 16:20 ` Arnd Bergmann
2015-12-29 16:20 ` Arnd Bergmann
2015-12-29 16:30 ` Santosh Shukla
2015-12-29 16:30 ` Santosh Shukla
[not found] ` <CAAyOgsYuMWudLgbSNM+QAkSXpU_fp6Ue01r=Ufmf5MXUHMs4UQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-12-29 17:31 ` Alex Williamson
2015-12-29 17:31 ` Alex Williamson
[not found] ` <1451410269.18084.15.camel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2015-12-31 9:33 ` Santosh Shukla
2015-12-31 9:33 ` Santosh Shukla
[not found] ` <CAAyOgsaxEaQ5+BW6Rwmz4cEuzVUdswZAWyF0OrbdPpXduwESYg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-12-31 15:41 ` Alex Williamson
2015-12-31 15:41 ` Alex Williamson
2016-01-07 9:31 ` Santosh Shukla
2014-05-10 7:07 ` Jann Horn
2014-05-10 7:07 ` Jann Horn
[not found] ` <20140510070742.GE6099-7cfQGs147y6a6lf8Wg2v7Z5kstrrjoWp@public.gmane.org>
2014-05-10 19:32 ` Josh Triplett
2014-05-10 19:32 ` Josh Triplett
2014-05-11 12:50 ` Jann Horn
[not found] ` <20140511125006.GA16197-7cfQGs147y6a6lf8Wg2v7Z5kstrrjoWp@public.gmane.org>
2014-05-11 21:05 ` Josh Triplett
2014-05-11 21:05 ` Josh Triplett
2014-06-01 10:35 ` Maciej W. Rozycki
2014-06-01 10:35 ` Maciej W. Rozycki
2014-06-04 22:59 ` H. Peter Anvin
[not found] ` <538FA4C7.2050206-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2014-06-06 9:02 ` Maciej W. Rozycki
2014-06-06 9:02 ` Maciej W. Rozycki
2014-05-10 17:18 ` Greg Kroah-Hartman
2014-05-10 17:18 ` Greg Kroah-Hartman
[not found] ` <20140510171845.GA799-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2014-05-10 19:36 ` Josh Triplett
2014-05-10 19:36 ` Josh Triplett
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