linux-kernel - Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports

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Date:	Fri, 09 May 2014 14:20:45 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Josh Triplett <josh@...htriplett.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit
 and 32-bit ports

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


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