From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45071) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dUcdi-0008Aa-Ps for qemu-devel@nongnu.org; Mon, 10 Jul 2017 13:38:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dUcdf-0007NO-Lv for qemu-devel@nongnu.org; Mon, 10 Jul 2017 13:38:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33522) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dUcdf-0007NA-Cf for qemu-devel@nongnu.org; Mon, 10 Jul 2017 13:38:27 -0400 Date: Mon, 10 Jul 2017 14:38:21 -0300 From: Eduardo Habkost Message-ID: <20170710173821.GD5167@localhost.localdomain> References: <20170703113940.0e0415a2@nial.brq.redhat.com> <0efc917e-16d3-f01b-6fd8-a3bb71580bf4@ilande.co.uk> <20170707133320.2e0d741d@nial.brq.redhat.com> <1b4f1872-2ea2-8c10-593f-e2adf013b234@ilande.co.uk> <20170707164453.4ba325fd@nial.brq.redhat.com> <20170707150707.GJ10776@localhost.localdomain> <58f2d98e-ae7e-e2e7-e7f3-68e937b0b79f@ilande.co.uk> <20170710100147.0a7339e4@nial.brq.redhat.com> <20170710145331.GJ12152@localhost.localdomain> <20170710172336.33c64f86@nial.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170710172336.33c64f86@nial.brq.redhat.com> Subject: Re: [Qemu-devel] [PATCHv7 5/6] fw_cfg: move qdev_init_nofail() from fw_cfg_init1() to callers List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: peter.maydell@linaro.org, mst@redhat.com, somlo@cmu.edu, Mark Cave-Ayland , qemu-devel@nongnu.org, rjones@redhat.com, pbonzini@redhat.com, lersek@redhat.com On Mon, Jul 10, 2017 at 05:23:36PM +0200, Igor Mammedov wrote: > On Mon, 10 Jul 2017 11:53:31 -0300 > Eduardo Habkost wrote: > > > On Mon, Jul 10, 2017 at 10:01:47AM +0200, Igor Mammedov wrote: > > > On Fri, 7 Jul 2017 17:20:25 +0100 > > > Mark Cave-Ayland wrote: > > > > > > > On 07/07/17 16:07, Eduardo Habkost wrote: > > > > > > > > >> looks fine, > > > > >> > > > > >> so what I'd do is: > > > > >> * drop 4/6 > > > > > > > > Yes. > > > > > > > > > Agreed on this point. But: > > > > > > > > > >> * make fw_cfg_find() use ambiguous argument and error_abort if ambiguous == true > > > > > > > > During my latest tests I've found that everything works fine without the > > > > ambiguous argument. > > > > > > > > Do we still want to keep it? And I don't think error_abort() is the > > > > right thing to do here, I'd much rather return NULL and add a suitable > > > > comment. > > > I'd still use ambiguous argument and since you prefer not to assert > > > I'd add errp argument to fw_cfg_find() and handle error at callsites. > > > > > > Just returning NULL isn't sufficient if you need to distinguish > > > 'not found' vs 'duplicate' usecases, additionally 'not found' > > > in most cases isn't even error but 'duplicate' definitely is. > > > > > > Aborting on diplicate in fw_cfg_find() is fine and would > > > help to avoid touching current callers if you wish to limit > > > patches scope, but you can go with proper error propagating > > > route if you wish. > > > > Just making realize refuse to create two devices sounds much > > simpler to me. No need to make fw_cfg_find() more complex (if we > > add errp argument to it) or less useful (if we add > > assert(!ambiguous) to it). > the problem here was a error message to print if fw_cfg_find() > returns NULL for missing or duplicate, if we need to print > precise error we would need proper error handling. I don't see where we would need a precise error message, except for realizefn (where the only case fw_cfg_find() would return NULL is for duplicate devices). > > Considering to fw_cfg is builtin device I'd prefer just > assert in fw_cfg_find() on duplicate (all the callers consider it as error) > and let developer to deal with assert if it is triggered. Except that it would make it more difficult for realizefn to return a proper error message. Anyway, I am not completely against adding assert(!ambiguous) to fw_cfg_find() if Mark wants to follow your advice. I just think it's not necessary. I will only continue discussing this if I see issues in the next version of the series. -- Eduardo