Hi Oleksij, On 06/15/2017 08:56 AM, Oleksij Rempel wrote: > Hi Vladimir, > > On Sun, Jun 11, 2017 at 10:57:18PM +0300, Vladimir Zapolskiy wrote: >> Hi Oleksij, >> >> On 06/11/2017 09:19 AM, Oleksij Rempel wrote: >>> Hi Rob, >>> >>> On Fri, Jun 09, 2017 at 10:41:30AM -0500, Rob Herring wrote: >>>> On Fri, Jun 9, 2017 at 9:16 AM, Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx> wrote: >>>>> This property is needed for barebox or may be other bootloaders >>>>> to set proper gpio configuration as early as possible. >>>>> >>>>> This example is mainly based on "lines-initial-states" property >>>>> from this binding documentation: >>>>> Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt >>>> >>>> Don't we have a binding for this already based on gpio-hogs. >>> >>> Markus Pargmann was working on this topic before and suddenly was not >>> able to finish it. >> >> that's fine, but the proposed extension is supposedly not wanted. > > :( No worries, we're in the discussion and 'supposedly' was a meaningful word :) >>> I found only some not finished discussions and no code or documentation >>> in linux kernel upstream. >>> >>> So far, I was able to find fallowing patches and discussions: >>> patch 23.08.2015, last comment 11.05.2017: >>> https://patchwork.kernel.org/patch/7096721/ >>> >>> patch 23.02.2016, last comment 09.03.2016: >>> https://patchwork.ozlabs.org/patch/586743/ >>> >>> Since there was objections about node-like design for gpio-initval, I >>> provided an array property, which is similar to initval properties already used >>> for different other device nodes. For example: >>> >>> Documentation/devicetree/bindings/net/wireless/qcom,ath10k.txt >>> qcom,ath10k-calibration-data >>> >>> Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt >>> lines-initial-states >> >> It'd rather be better to fix the drivers and remove the properties >> from these found device tree binding descriptions. > > no sure if it is possible. WiFi calibration data is kind of initval too. Sorry, I have no idea about the ath10k calibration data and its connection to the GPIO framework. >>> >>> Please fixme if I miss something. >> >> Why is GPIO hogging mechanism not good enough for your purpose? > > Becouse it should not permanently hog a gpio. The "Hogging" should be > released as soon as some driver will request it. > > Right now, if I define gpio-hog, boot loader will configure it and start > linux. But linux will never let it free. > > If you have other suggestions which fit to this use case, please tell > me. I assume, right now I'm just blind. Ok, I'll meditate on it. > Other way, I can imagine is to create real device nodes which use this > gpios. Compatible for this devices will be like this: > some_gpio_holder: gpio@0 { > compatible = "gpio-for-userspace"; > gpio = <&gpio1 5 GPIO_ACTIVE_HIGH>; > }; Generally it might be a good option, because if GPIOs are essentially needed to be preset, I can conclude there are some ICs to which these GPIOs are connected, thus drivers of these ICs can become GPIO consumers and get a proper description in a board DTB. > > Boot loader will configure it as needed, an linux will do nothing with > it so it can be used over /dev/gpio interface. As I read it from Documentation/gpio/sysfs.txt generic interface(s) to control GPIOs is a last resort, it is not clear if you want a new feature for all possible consumers or just userspace consumers. -- With best wishes, Vladimir -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
