From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" 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 Message-ID: <536D46AD.3070608@zytor.com> References: <20140509191914.GA7286@jtriplet-mobl1> <9233735.5FfZoZovqP@wuerfel> <536D406D.2080508@zytor.com> <4366326.1D6xUnlac7@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4366326.1D6xUnlac7@wuerfel> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Arnd Bergmann Cc: Josh Triplett , Greg Kroah-Hartman , akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org 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