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[2001:470:b8f6:1b::1]) by smtp.gmail.com with ESMTPSA id h24sm5501853otg.20.2021.04.07.07.28.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Apr 2021 07:28:30 -0700 (PDT) Sender: Corey Minyard Received: from minyard.net (unknown [IPv6:2001:470:b8f6:1b:f036:ecd9:2bd0:ef09]) by serve.minyard.net (Postfix) with ESMTPSA id 89595180570; Wed, 7 Apr 2021 14:28:29 +0000 (UTC) Date: Wed, 7 Apr 2021 09:28:28 -0500 From: Corey Minyard To: Quan Nguyen Cc: Rob Herring , Joel Stanley , Andrew Jeffery , Wolfram Sang , Philipp Zabel , openipmi-developer@lists.sourceforge.net, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, openbmc@lists.ozlabs.org, Open Source Submission , Phong Vo , "Thang Q . Nguyen" Subject: Re: [PATCH v2 0/3] Add Aspeed SSIF BMC driver Message-ID: <20210407142828.GE7166@minyard.net> Reply-To: minyard@acm.org References: <20210330141029.20412-1-quan@os.amperecomputing.com> <20210402142124.GV507977@minyard.net> <0e7fceff-4a01-5cb0-72eb-8b47d598f1c3@os.amperecomputing.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0e7fceff-4a01-5cb0-72eb-8b47d598f1c3@os.amperecomputing.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 07, 2021 at 08:09:50PM +0700, Quan Nguyen wrote: > Hi Corey, > > Thank you for reviewing > I'll put my respond inline below. > > -Quan > > On 02/04/2021 21:21, Corey Minyard wrote: > > On Tue, Mar 30, 2021 at 09:10:26PM +0700, Quan Nguyen wrote: > > > This series add support for the Aspeed specific SSIF BMC driver which > > > is to perform in-band IPMI communication with the host in management > > > (BMC) side. > > > > I don't have any specific feedback for this, but I'm wondering if it's > > really necessary. > > > > Why can't the BMC just open the I2C device and use it? Is there any > > functionality that this provides that cannot be accomplished from > > userland access to the I2C device? I don't see any. > > > > If it tied into some existing framework to give abstract access to a BMC > > slave side interface, I'd be ok with this. But I don't see that. > > > > The SSIF at the BMC side acts as an I2C slave and we think that the kernel > driver is unavoidable to handle the I2c slave events > (https://www.kernel.org/doc/html/latest/i2c/slave-interface.html) > > And to make it works with existing OpenBMC IPMI stack, a userspace part, > ssifbridge, is needed (https://github.com/openbmc/ssifbridge). This > ssifbridge is to connect this driver with the OpenBMC IPMI stack so the IPMI > stack can communicate via SSIF channel in similar way that was implemented > with BT and KCS (ie: btbridge/kcsbridge and its corespondent kernel drivers > (https://github.com/openbmc/btbridge and > https://github.com/openbmc/kcsbridge)) Dang, I don't know why there's not a generic userland interface for the slave. And I've made this mistake before :(. Anyway, you are right, you need a driver. I'll review. -corey > > > Unless there is a big need to have this in the kernel, I'm against > > including this and would suggest you do all this work in userland. > > Perhaps write a library. Sorry, but I'm trying to do my part to reduce > > unnecessary things in the kernel. > > > > Thanks, > > > > -corey > >