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Thu, 8 Oct 2020 07:21:53 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id A35F5F80163; Thu, 8 Oct 2020 07:21:51 +0200 (CEST) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id C8D4DF80167 for ; Thu, 8 Oct 2020 07:21:43 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz C8D4DF80167 Authentication-Results: alsa1.perex.cz; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="RBF3g3Cs" Received: from localhost (unknown [213.57.247.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E1CA720659; Thu, 8 Oct 2020 05:21:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602134501; bh=vJb76P79pOLUgt2vBkS0qzTujOiqXJm1lL7ssRNU9Es=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RBF3g3CswRDNpEr82rgRvvml4H/p0PJrI5Ff7RKqRDparZzSHv5o/iTC1uVIQmRXv SQ1HkXq3Kn2lUR0tfsdQ4jZEJNh7QhXkUg7zgdC7hN21Etd3u4akovBCK/Igrecsdo BFWxC6epCnv+/951Ucd5ZOuQQAw2NQjjj7nUt7so= Date: Thu, 8 Oct 2020 08:21:37 +0300 From: Leon Romanovsky To: "Ertman, David M" Subject: Re: [PATCH v2 1/6] Add ancillary bus support Message-ID: <20201008052137.GA13580@unreal> References: <20201005182446.977325-1-david.m.ertman@intel.com> <20201005182446.977325-2-david.m.ertman@intel.com> <20201006071821.GI1874917@unreal> <20201006170241.GM1874917@unreal> <20201007192610.GD3964015@unreal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Cc: "alsa-devel@alsa-project.org" , "parav@mellanox.com" , "tiwai@suse.de" , "netdev@vger.kernel.org" , Pierre-Louis Bossart , "ranjani.sridharan@linux.intel.com" , "fred.oh@linux.intel.com" , "linux-rdma@vger.kernel.org" , "dledford@redhat.com" , "broonie@kernel.org" , Parav Pandit , Jason Gunthorpe , "gregkh@linuxfoundation.org" , "kuba@kernel.org" , "Williams, Dan J" , "Saleem, Shiraz" , "davem@davemloft.net" , "Patil, Kiran" X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Wed, Oct 07, 2020 at 08:46:45PM +0000, Ertman, David M wrote: > > -----Original Message----- > > From: Parav Pandit > > Sent: Wednesday, October 7, 2020 1:17 PM > > To: Leon Romanovsky ; Ertman, David M > > > > Cc: Pierre-Louis Bossart ; alsa- > > devel@alsa-project.org; parav@mellanox.com; tiwai@suse.de; > > netdev@vger.kernel.org; ranjani.sridharan@linux.intel.com; > > fred.oh@linux.intel.com; linux-rdma@vger.kernel.org; > > dledford@redhat.com; broonie@kernel.org; Jason Gunthorpe > > ; gregkh@linuxfoundation.org; kuba@kernel.org; Williams, > > Dan J ; Saleem, Shiraz > > ; davem@davemloft.net; Patil, Kiran > > > > Subject: RE: [PATCH v2 1/6] Add ancillary bus support > > > > > > > From: Leon Romanovsky > > > Sent: Thursday, October 8, 2020 12:56 AM > > > > > > > > This API is partially obscures low level driver-core code and needs > > > > > to provide clear and proper abstractions without need to remember > > > > > about put_device. There is already _add() interface why don't you do > > > > > put_device() in it? > > > > > > > > > > > > > The pushback Pierre is referring to was during our mid-tier internal > > > > review. It was primarily a concern of Parav as I recall, so he can speak to > > his > > > reasoning. > > > > > > > > What we originally had was a single API call > > > > (ancillary_device_register) that started with a call to > > > > device_initialize(), and every error path out of the function performed a > > > put_device(). > > > > > > > > Is this the model you have in mind? > > > > > > I don't like this flow: > > > ancillary_device_initialize() > > > if (ancillary_ancillary_device_add()) { > > > put_device(....) > > > ancillary_device_unregister() > > Calling device_unregister() is incorrect, because add() wasn't successful. > > Only put_device() or a wrapper ancillary_device_put() is necessary. > > > > > return err; > > > } > > > > > > And prefer this flow: > > > ancillary_device_initialize() > > > if (ancillary_device_add()) { > > > ancillary_device_unregister() > > This is incorrect and a clear deviation from the current core APIs that adds the > > confusion. > > > > > return err; > > > } > > > > > > In this way, the ancillary users won't need to do non-intuitive put_device(); > > > > Below is most simple, intuitive and matching with core APIs for name and > > design pattern wise. > > init() > > { > > err = ancillary_device_initialize(); > > if (err) > > return ret; > > > > err = ancillary_device_add(); > > if (ret) > > goto err_unwind; > > > > err = some_foo(); > > if (err) > > goto err_foo; > > return 0; > > > > err_foo: > > ancillary_device_del(adev); > > err_unwind: > > ancillary_device_put(adev->dev); > > return err; > > } > > > > cleanup() > > { > > ancillary_device_de(adev); > > ancillary_device_put(adev); > > /* It is common to have a one wrapper for this as > > ancillary_device_unregister(). > > * This will match with core device_unregister() that has precise > > documentation. > > * but given fact that init() code need proper error unwinding, like > > above, > > * it make sense to have two APIs, and no need to export another > > symbol for unregister(). > > * This pattern is very easy to audit and code. > > */ > > } > > I like this flow +1 > > But ... since the init() function is performing both device_init and > device_add - it should probably be called ancillary_device_register, > and we are back to a single exported API for both register and > unregister. > > At that point, do we need wrappers on the primitives init, add, del, > and put? Let me summarize. 1. You are not providing driver/core API but simplification and obfuscation of basic primitives and structures. This is new layer. There is no room for a claim that we must to follow internal API. 2. API should be symmetric. If you call to _register()/_add(), you will need to call to _unregister()/_del(). Please don't add obscure _put(). 3. You can't "ask" from users to call internal calls (put_device) over internal fields in ancillary_device. 4. This API should be clear to drivers authors, "device_add()" call (and semantic) is not used by the drivers (git grep " device_add(" drivers/). Thanks > > -DaveE