From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59042) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WSNeC-0007m9-GS for qemu-devel@nongnu.org; Tue, 25 Mar 2014 05:27:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WSNe5-0002FG-Dt for qemu-devel@nongnu.org; Tue, 25 Mar 2014 05:27:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62551) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WSNe5-0002D8-5p for qemu-devel@nongnu.org; Tue, 25 Mar 2014 05:27:45 -0400 Date: Tue, 25 Mar 2014 11:27:51 +0200 From: "Michael S. Tsirkin" Message-ID: <20140325092751.GB24194@redhat.com> References: <1395671853-2685-1-git-send-email-mst@redhat.com> <1395671853-2685-4-git-send-email-mst@redhat.com> <20140324171115.GI3829@work-vm> <20140324215027.GA15488@redhat.com> <20140325092313.GB2459@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140325092313.GB2459@work-vm> Subject: Re: [Qemu-devel] [RFC v2 3/5] vmstate: add VMS_MUST_EXIST List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: Peter Maydell , qemu-devel@nongnu.org On Tue, Mar 25, 2014 at 09:23:13AM +0000, Dr. David Alan Gilbert wrote: > * Michael S. Tsirkin (mst@redhat.com) wrote: > > On Mon, Mar 24, 2014 at 05:11:16PM +0000, Dr. David Alan Gilbert wrote: > > > > > > I think your intent here is just to misuse the field_exist function pointer > > > as a call for a different reason as a hook for a validator; is it really worth > > > misusing it like that or is something more explicit worth it? > > > Perhaps something passed an Error** so it could pass back what was wrong? > > > > > > Well adding a required field seems valuable by itself, does it not? > > Maybe; however most fields are always-present, unless they have a test > function or minimum version, so it's a little weird to add a 'required' > when that's the default. Right - here we say "there is a test function but it must return true". I considered adding a separate callback but it worried me that it's not clear how would it interact with the exist flag or the version flag. Ideas? > > And there's no way to pass in Error** since none of the callers > > has Error**: all of migration still uses stderr to pass > > errors. > > > > So we could add an API but it doesn't seem too valuable. > > > > Since all callers will use this through a wrapper like VMSTATE_TEST, > > it will be easy to change our mind later. > > Yep, that's fine - was just an idea. > > Dave > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK