Messages in this thread | | | Date | Thu, 10 Mar 2016 12:37:32 +0530 | From | Laxman Dewangan <> | Subject | Re: [PATCH 4/5] gpio: of: Add support to have multiple gpios in gpio-hog |
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On Wednesday 09 March 2016 10:47 PM, Stephen Warren wrote: > On 03/09/2016 06:20 AM, Laxman Dewangan wrote: >> >> On Wednesday 09 March 2016 11:58 AM, Markus Pargmann wrote: >>> * PGP Signed by an unknown key >>> >>> Hi, >>> >>> On Tue, Mar 08, 2016 at 05:32:07PM +0530, Laxman Dewangan wrote: >>>> The child node for gpio hogs under gpio controller's node >>>> provide the mechanism to automatic GPIO request and >>>> configuration as part of the gpio-controller's driver >>>> probe function. >>>> >>>> Currently, property "gpio" takes one gpios for such >>>> configuration. Add support to have multiple GPIOs in >>>> this property so that multiple GPIOs of gpio-controller >>>> can be configured by this mechanism with one child node. >>> So if I read this correctly you want to have multiple GPIOs with the >>> same line name? Why don't you use multiple child nodes with individual >>> line names? >>> >> There is cases on which particular functional configuration needs sets >> of GPIO to set. On this case, making sub node for each GPIOs creates >> lots of sub-nodes and add complexity on readability, usability and >> maintainability. >> Example: for my board, I wanted to set GPIO H2 to input and H0 and H1 to >> be output high. >> Instead of three nodes, I can have two here: >> gpio@0,6000d000 { >> wlan_input { >> gpio-hog; >> gpios = <TEGRA_GPIO(H, 2) 0>; >> input; >> }; >> >> wlan_output { >> gpio-hog; >> gpios = <TEGRA_GPIO(H, 0) 0 TEGRA_GPIO(H, 1) 0>; >> output-high; >> }; >> }; > > >> So here I am grouping the multiple output GPIO together. >> >> This looks much similar if we have many GPIOs for one type of >> configurations. >> >> Even it looks better if we have something: >> gpio@0,6000d000 { >> wlan_control { >> gpio-hog; >> gpios-input = <TEGRA_GPIO(H, 2) 0>; >> gpios-output-high = <TEGRA_GPIO(H, 0) 0 >> TEGRA_GPIO(H, 1) 0>; >> }; >> }; > > The problem with that is the description used when acquiring the GPIO > is just "wlan_input", "wlan_output", or "wlan_control". There's > nothing to indicate what those individual pins do (perhaps one is a > reset signal, one is a regulator enable, etc.?) By requiring separate > nodes for each GPIO, then the node name can provide a meaningful > semantic name/description for each GPIO, which provides much more > information. >
On this case, we have already property "line-name" and passed the name of the gpio via this property. The property names is "line-name" which is good for one string. We can support other property "line-names" with multiple string per GPIO index.
line-names = "wlan-reset", "wlan-enable";
> If the approach in this patch is acceptable though, I think you want > to update the description of "gpios" (in the GPIO hog definition > section) in Documentation/devicetree/bindings/gpio/gpio.txt to mention > that multiple GPIO entries are legal. Right now it says that property > much contain exactly #gpio-cells, not a multiple of #gpio-cells.
I have 5th patch for this and will rearrange series as you suggested on 5th patch.
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