From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 22 Mar 2018 10:04:51 +0100 From: Greg KH To: Darren Hart Cc: Vadim Pasternak , andy.shevchenko@gmail.com, platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org, jiri@resnulli.us, michaelsh@mellanox.com, Wolfram Sang , linux-i2c@vger.kernel.org Subject: Re: [PATCH v1 2/4] platform/x86: mlx-platform: Add differed bus functionality Message-ID: <20180322090451.GA22313@kroah.com> References: <1518559776-188942-1-git-send-email-vadimp@mellanox.com> <1518559776-188942-3-git-send-email-vadimp@mellanox.com> <20180321225818.GA23931@fury> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180321225818.GA23931@fury> User-Agent: Mutt/1.9.4 (2018-02-28) X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, Mar 21, 2018 at 03:58:18PM -0700, Darren Hart wrote: > On Tue, Feb 13, 2018 at 10:09:34PM +0000, Vadim Pasternak wrote: > > Add deferred bus functionality in order to enforce probing flow execution > > order. Driver mlx-platform activates platform driver i2c-mux-reg, which > > creates busses infrastructure, after that it activates mlxreg-hotplug > > driver, which uses these busses, for connecting devices. The possible > > miss-ordering can happened, for example in case the probing routine of > > mlxreg-hotplug is already started execution, while i2c-mux-reg probing > > routine is not completed yet. In such situation the first one could > > attempt to connect device to adapter number, which is not created yet. > > And as a result this connection will fail. In order to ensure the order of > > probing execution on mlxreg-hotplug probe routine will be deferred until > > all the busses is not created by probe routine of i2c-mux-reg. > > In order to ensure the flow order, mlx-platform driver passes the highest > > bus number to the mlxreg-hotplug platform data, which in their turn could > > wait in the deferred state, until all the necessary buses topology is not > > exist. > > Vadim, > > I've got part way through a review of this series several times, and keep > running out of time trying to determine if the solution is appropriate > for the problem. > > The deferred probing waiting for the i2c bus to be available seems like > something we might be able to handle more elegantly with: > > 1) request_module() in the platform driver > 2) careful use of init levels (subsys, device, late) > > This isn't something I'm well versed in - so I'll reach out here for > some advice from Greg and the i2c maintainer, Wolfram, and list (added > to Cc). deferred device probe?