From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52535) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g0pMY-0001Hc-5p for qemu-devel@nongnu.org; Fri, 14 Sep 2018 10:46:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1g0pMU-0002jF-PU for qemu-devel@nongnu.org; Fri, 14 Sep 2018 10:46:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37814) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1g0pMU-0002hl-II for qemu-devel@nongnu.org; Fri, 14 Sep 2018 10:46:22 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2A89E300273D for ; Fri, 14 Sep 2018 14:46:21 +0000 (UTC) Date: Fri, 14 Sep 2018 15:46:15 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20180914144614.GC3081@work-vm> References: <20180914104835.26019-1-kraxel@redhat.com> <20180914113407.GB3081@work-vm> <20180914125400.nvq5t3pjh326pvr4@sirius.home.kraxel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180914125400.nvq5t3pjh326pvr4@sirius.home.kraxel.org> Subject: Re: [Qemu-devel] [PATCH v2] usb: assign unique serial numbers to hid devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gerd Hoffmann Cc: qemu-devel@nongnu.org * Gerd Hoffmann (kraxel@redhat.com) wrote: > Hi, > > > OK, so now I've found the bit about the magic 42; commit 7b074a22 of > > yours; recommended checking for 42 for knowing we had autosuspend; > > what's actually in the current fedora hid rules is serial!=1 - I wonder > > what others have. > > Whatever upstream systemd/udev has I guess ... > > A bit of history ... > > * First there was nothing. > * Then I added a rule to udev checking for serial == 42 > (this is in rhel-6). > * Then systemd + udev merged. > * Then I changed the rule to check for serial != 1 instead, so we can > use any serial but "1" which is the one the old broken devices had > (this is in rhel-7). March 2014 in upstream systemd. > * Then all usb power management rules where dropped from systemd (June > 2015). Which I figured today, after wondering that the rules are > gone in fedora 28. > > So, three years ago the serial number check was dropped upstream, yet I > hav't seen a single report about autosuspend issues (or cpu usage for > usb emulation going up, which is the typical symtom). > > So I figured I can stop worring that changing the serial number will > break things and just do it. > > And even if it turns out autosuspend is still an issue: I think > meanwhile we can really stop worrying about guests running in old qemu > versions with broken usb suspend (fixed in 0.13 !). If needed we can > enable autosuspend unconditionally in guests. OK, so what about the other question - which serial number do we end up with after this patch; do we get the 89126/28754/68284 or do we get the path based one from your change that calls usb_desc_create_serial? Dave > cheers, > Gerd > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK