From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Brezillon Subject: Re: [PATCH v2 2/7] i3c: Add core I3C infrastructure Date: Tue, 27 Feb 2018 22:14:07 +0100 Message-ID: <20180227221407.0cd7f8a9@bbrezillon> References: <20171214151610.19153-1-boris.brezillon@free-electrons.com> <20171214151610.19153-3-boris.brezillon@free-electrons.com> <20180223213000.407461d2@bbrezillon> <1b8fe82f-079b-6f55-0e59-5773027faa8e@synopsys.com> <20180226213607.7161bb0a@bbrezillon> <20180227211302.26f76427@bbrezillon> 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: Przemyslaw Sroka Cc: Vitor Soares , Boris Brezillon , Wolfram Sang , "linux-i2c@vger.kernel.org" , Jonathan Corbet , "linux-doc@vger.kernel.org" , Greg Kroah-Hartman , Arnd Bergmann , Arkadiusz Golec , Alan Douglas , Bartosz Folta , Damian Kos , Alicja Jurasik-Urbaniak , Cyprian Wronka , Suresh Punnoose , Thomas Petazzoni , Nishanth Menon , Rob Herring , Pawel Moll List-Id: linux-i2c@vger.kernel.org On Tue, 27 Feb 2018 20:24:43 +0000 Przemyslaw Sroka wrote: > > > SETDASA is simply faster than ENTDAA, but only if there is no > > > need to collect BCR/DCR/PID of such devices. I think most > > > applications would like to have them as an status information so > > > after all ENTDAA can be regarded as an generic approach (unless > > > I'm mistaken). > > > > Actually, we could retrieve BCR/DCR/PID (and all other relevant > > information, like MAXDS) even with the SETDASA approach. We just > > need to send the according CCC commands after SETDASA. > > > I agree, what I meant by "SETDASA is simply faster than ENTDAA, but > only if there is no need to collect BCR/DCR/PID of such devices." Is > that it is faster than DAA but only if not followed by GET CCC > commands to gather BCR/DCR/PID. I think we are on the same page here. Yes, but right now it's not the case, see my other reply ;-). > > > But that's also my understanding that ENTDAA should always work, and > > SETDASA usage is only needed if you want to reserve a dynamic > > address and assign it to a device before DAA takes place. This way > > you can enforce the device priority (WRT IBIs). But honestly, > > that's the only use case I can think of, and to me, it sounds like > > an advanced feature we may want to support at some point, but don't > > need in the initial implementation. > Still ENTDAA seems to be sufficient for IBI prioritization but I can > imagine some use cases where people would like to use it for such > purposes. Note that SETDASA is applicable only for devices with SA so > it is self-explanatory that it cannot be considered as utility to > define priorities for all devices before ENTDAA. We have SETNEWDA for other use cases: say you want one of your device to have an higher priority, you can just manually set a new dynamic address that is lower than any other devices on the bus (I plan to expose that through sysfs, by making the address file writable). -- Boris Brezillon, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com