Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934438AbaGPOTC (ORCPT ); Wed, 16 Jul 2014 10:19:02 -0400 Received: from mail-qa0-f52.google.com ([209.85.216.52]:48833 "EHLO mail-qa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759250AbaGPOS6 (ORCPT ); Wed, 16 Jul 2014 10:18:58 -0400 MIME-Version: 1.0 In-Reply-To: <5214160.a78RDYzY5T@wuerfel> References: <1405071167-14503-1-git-send-email-jaswinder.singh@linaro.org> <5461658.P0nNPHkj0L@wuerfel> <5214160.a78RDYzY5T@wuerfel> Date: Wed, 16 Jul 2014 19:48:57 +0530 Message-ID: Subject: Re: [PATCHv8 2/2] mailbox: Introduce framework for mailbox From: Jassi Brar To: Arnd Bergmann Cc: Sudeep Holla , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "ks.giri@samsung.com" , "ijc+devicetree@hellion.org.uk" , Mark Rutland , "robh+dt@kernel.org" , Pawel Moll , "courtney.cavin@sonymobile.com" , "mporter@linaro.org" , "slapdau@yahoo.com.au" , "lftan.linux@gmail.com" , "loic.pallardy@st.com" , "s-anna@ti.com" , "ashwin.chaugule@linaro.org" , "bjorn@kryo.se" , "patches@linaro.org" , "Mollie.Wu@tw.fujitsu.com" , "t.takinishi@jp.fujitsu.com" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16 July 2014 19:38, Arnd Bergmann wrote: > On Wednesday 16 July 2014 18:42:22 Jassi Brar wrote: >> On 16 July 2014 18:39, Arnd Bergmann wrote: >> > On Wednesday 16 July 2014 18:35:33 Jassi Brar wrote: >> >> On 16 July 2014 18:15, Arnd Bergmann wrote: >> >> > On Wednesday 16 July 2014 18:07:04 Jassi Brar wrote: >> >> >> On 16 July 2014 15:46, Arnd Bergmann wrote: >> >> >> > On Wednesday 16 July 2014 10:40:19 Sudeep Holla wrote: >> >> >> >> > + >> >> >> >> > +Required property: >> >> >> >> > +- mbox: List of phandle and mailbox channel specifier. >> >> >> >> > + >> >> >> >> > +- mbox-names: List of identifier strings for each mailbox channel >> >> >> >> > + required by the client. >> >> >> >> > + >> >> >> >> >> >> >> >> IMO the mailbox names are more associated with the controller channels/ >> >> >> >> mailbox rather than the clients using it. Does it make sense to move >> >> >> >> this under controller. It also avoid each client replicating the names. >> >> >> > >> >> >> > I think it would be best to just make the mbox-names property optional, >> >> >> > like we have for other subsystems. >> >> >> > >> >> >> A very similar subsystem - DMAEngine also has 'dma-names' as a >> >> >> required property. >> >> >> >> >> >> If a client is assigned only 1 mbox in DT, we can do without >> >> >> mbox-names. But I am not sure what to do if a client needs two or more >> >> >> differently capable mboxes? Simply allocating in order of mbox request >> >> >> doesn't seem very robust. >> >> > >> >> > Traditionally, these things (regs, interrupts, ...) are just accessed >> >> > by index. The reason why dmaengine requires the name is that some machines >> >> > can use multiple DMA engine devices attached to the same request line, >> >> > so the dmaengine subsystem can pick any of them that has a matching >> >> > name. >> >> And also, I think, when a client needs 2 different dma channels, say >> >> for RX and TX each. The api can't assign the first channel specified >> >> in 'dmas' property to the first channel request that comes to it, >> >> unless we assume client driver always requests dma channels in the >> >> order written in its DT node. And this is the main reason I see for >> >> having mbox-names property. >> > >> > Most subsystems require passing an explicit index in this case. >> > >> >> If we make mbox-names optional, do we assume client driver must >> >> request mbox in the order specified in its DT node? >> > >> > Correct. >> > >> OK. So how about we drop mbox-names altogether and expect client >> driver to simply provide an index of the mbox needed? > > That would be fine with me, but I think a lot of people like > the idea of identifying things by name, and are used to that > from the other subsystems. > > Maybe you can leave the mbox-names property defined as 'optional' > in the generic mbox binding but remove the code in Linux? That way > we can always put it back at a later point without changing the > binding in an incompatible way. > > Individual mailbox clients can mandate specific strings. > Sounds great. Thanks Jassi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/