From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Jones Subject: Re: [PATCH v4 2/5] mfd: lm3533: Support initialization from Device Tree Date: Mon, 9 Jan 2017 08:36:38 +0000 Message-ID: <20170109083638.GB2155@dell> References: <20161226181153.11271-1-bjorn.andersson@linaro.org> <20161226181153.11271-2-bjorn.andersson@linaro.org> <20170104115424.GH27589@dell> <20170104192608.GN10531@minitux> <20170105074952.GG24225@dell> <20170105163054.GO10531@minitux> <20170106095349.GE9851@dell> <20170106185422.GQ10531@minitux> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <20170106185422.GQ10531@minitux> Sender: linux-iio-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bjorn Andersson Cc: Rob Herring , Mark Rutland , Jonathan Cameron , Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , Richard Purdie , Jacek Anaszewski , Pavel Machek , Jingoo Han , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-leds-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Bjorn Andersson List-Id: devicetree@vger.kernel.org On Fri, 06 Jan 2017, Bjorn Andersson wrote: > On Fri 06 Jan 01:53 PST 2017, Lee Jones wrote: > > > On Thu, 05 Jan 2017, Bjorn Andersson wrote: > > > > > On Wed 04 Jan 23:49 PST 2017, Lee Jones wrote: > > > > > > > On Wed, 04 Jan 2017, Bjorn Andersson wrote: > > > > > > > > > On Wed 04 Jan 03:54 PST 2017, Lee Jones wrote: > > > > > > > > > > > On Mon, 26 Dec 2016, Bjorn Andersson wrote: > > > > > > > > > > > > > From: Bjorn Andersson > > > > > > > > > > > > > > Implement support for initialization of the lm3533 driver core and > > > > > > > probing child devices from Device Tree. > > > > > > > > > > > > > > > > > [..] > > > > > > > > > > > > @@ -512,6 +514,11 @@ static int lm3533_device_init(struct lm3533 *lm3533) > > > > > > > lm3533_device_bl_init(lm3533); > > > > > > > lm3533_device_led_init(lm3533); > > > > > > > > > > > > > > + if (lm3533->dev->of_node) { > > > > > > > + of_platform_populate(lm3533->dev->of_node, NULL, NULL, > > > > > > > + lm3533->dev); > > > > > > > + } > > > > > > > > > > > > I think it's save to call of_platform_populate(), even if !of_node. > > > > > > It will just fail and return an error code, which you are ignoring > > > > > > anyway. > > > > > > > > > > > > > > > > I thought so too, but that's apparently how you trigger probing children > > > > > of the root node. So we're stuck with a conditional. > > > > > > > > Ah, so this is to protect against the case where DT is present, but a > > > > node for this device is not (or is disabled), so is left unprobed. > > > > Then the bind is initiated via I2C? Or something else? > > > > > > > > > > In the event that a new lm3533 is spawned from sysfs we would not have > > > platform_data when entering lm3533_device_init() and just bail early. > > > > > > Therefor, this issue would be limited to the odd case of lm3533 being > > > initiated from code (e.g. a board file) on a DT enabled system. In which > > > case it will create and probe new devices from the root of the DT. > > > > Eewww, do we really want to support that? > > > > As long as we support non-DT probing of the driver this is a possible > scenario. And with modern ARM being DT-centric I think that if anyone > uses this driver with a modern version of the Linux kernel it's likely > that they would have this kind of hybrid solution. > > So, although ugly, I think we should keep this conditional and hope that > anyone using the driver will transition to use the DT binding. Very well, but can you add a comment describing the reason for its existence with a view to removing it further down the line? -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog