On Thu, Mar 22, 2018 at 03:18:40PM -0700, Darren Hart wrote: > On Thu, Mar 22, 2018 at 10:04:51AM +0100, Greg Kroah-Hartman wrote: > > 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? > > > > This patch series adds the following, which I believe is what you're referring > to Greg? : > > + /* Defer probing if the necessary adapter is not configured yet. */ > + deferred_adap = i2c_get_adapter(pdata->deferred_nr); > + if (!deferred_adap) > + return -EPROBE_DEFER; > > This is the preferred approach? Have the platform driver define the expected > adapter number, and then defer until that becomes available? Yes, that is what that interface is for, so it should work like this. But someone should test of course :) greg k-h
