From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCHv8 2/2] mailbox: Introduce framework for mailbox Date: Wed, 16 Jul 2014 15:09:11 +0200 Message-ID: <5461658.P0nNPHkj0L@wuerfel> References: <1405071167-14503-1-git-send-email-jaswinder.singh@linaro.org> <6436896.YqIi9fg7XW@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Jassi Brar 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.fujits List-Id: devicetree@vger.kernel.org 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. Arnd