From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v3 1/1] Shared memory uio_pci driver Date: Sun, 28 Mar 2010 13:31:23 +0300 Message-ID: <20100328103123.GC21749@redhat.com> References: <1269497376-21903-1-git-send-email-cam@cs.ualberta.ca> <4BAB30EE.4020509@redhat.com> <8286e4ee1003250924q7cca5e71u8b8b7c6d8b785eb8@mail.gmail.com> <4BAB90BB.5030401@redhat.com> <8286e4ee1003260914u5e6ceee2pf0c00590de182fb6@mail.gmail.com> <4BAE44F2.20801@redhat.com> <20100328074754.GA21749@redhat.com> <4BAF0D03.7060300@redhat.com> <20100328094006.GB21749@redhat.com> <4BAF251E.50609@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Cam Macdonell , kvm@vger.kernel.org, qemu-devel@nongnu.org To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:49894 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753068Ab0C1KfD (ORCPT ); Sun, 28 Mar 2010 06:35:03 -0400 Content-Disposition: inline In-Reply-To: <4BAF251E.50609@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Mar 28, 2010 at 12:45:02PM +0300, Avi Kivity wrote: > On 03/28/2010 12:40 PM, Michael S. Tsirkin wrote: >>>> uio accepts 32 bit writes to the char device file. We can encode >>>> the fd number there, and use the high bit to signal assign/deassign. >>>> >>>> >>> Ugh. Very unexpandable. >>> >> It currently fails on any non-4 byte write. >> So if we need more bits in the future we can always teach it >> about e.g. 8 byte writes. >> >> Do you think it's worth it doing it now already, and using >> 8 byte writes for msi mapping? >> > > Aren't ioctls a lot simpler? > > Multiplexing multiple functions on write()s is just ioctls done uglier. I don't have an opinion here. Writes do have an advantage that strace can show the buffer content without being patched. Further, something along the lines proposed above means that we do not need to depend in a system header to get the functionality. > -- > error compiling committee.c: too many arguments to function