Messages in this thread | | | Date | Mon, 07 Dec 2015 21:10:55 +0000 | From | Martyn Welch <> | Subject | Re: [PATCH 1/3] Device tree binding documentation for gpio-switch |
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On 07/12/15 17:37, Rob Herring wrote: > +Linus W > > On Fri, Dec 04, 2015 at 05:31:13PM +0000, Martyn Welch wrote: >> This patch adds documentation for the gpio-switch binding. This binding >> provides a mechanism to bind named links to gpio, with the primary >> purpose of enabling standardised access to switches that might be standard >> across a group of devices but implemented differently on each device. > > This is good and what I suggested, but it now makes me wonder if switch > is generic enough. This boils down to needing to expose single gpio > lines to userspace with a defined function/use. IIRC, there's been some > discussion about this before along with improving the userspace > interface for GPIO in general. So I'd like to get Linus' thoughts on > this. >
No problem. Rename gpio-signal?
> >> Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk> >> --- >> .../devicetree/bindings/misc/gpio-switch.txt | 47 ++++++++++++++++++++++ >> 1 file changed, 47 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/misc/gpio-switch.txt >> >> diff --git a/Documentation/devicetree/bindings/misc/gpio-switch.txt b/Documentation/devicetree/bindings/misc/gpio-switch.txt >> new file mode 100644 >> index 0000000..13528bd >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/misc/gpio-switch.txt >> @@ -0,0 +1,47 @@ >> +Device-Tree bindings for gpio attached switches. >> + >> +This provides a mechanism to provide a named link to specified gpios. This can >> +be useful in instances such as when theres a need to monitor a switch, which is >> +common across a family of devices, but attached to different gpios and even >> +implemented in different ways on differnet devices. >> + >> +Required properties: >> + - compatible = "gpio-switch"; >> + >> +Each signal is represented as a sub-node of "gpio-switch". The naming of >> +sub-nodes is arbitrary. >> + >> +Required sub-node properties: >> + >> + - label: Name to be given to gpio switch. >> + - gpios: OF device-tree gpio specification. >> + >> +Optional sub-node properties: >> + >> + - read-only: Boolean flag to mark the gpio as read-only, i.e. the line >> + should not be driven by the host. > > In terms a a switch use, allowing driving it would be an override of the > switch. Is that the idea here? >
Yeah - since it had become a lot more generic and a lot of switches/signals would probably be implemented with a pull-up resistor of something like that, it seemed to make sense to allow them to be driven as well.
>> + >> +Example nodes: >> + >> + gpio-switch { >> + compatible = "gpio-switch"; > > Both from a binding and driver perspective, there is no point in > grouping these. Each node can simply have this compatible string. >
True. I did it this way as this is how gpio-keys is implemented. OK, that has one optional parameter (autorepeat) for the block and this has none. Though I can also see that these probably have less in common than the individual lines used in gpio-keys.
>> + >> + write-protect { >> + label = "write-protect"; >> + gpios = <&gpx3 0 GPIO_ACTIVE_LOW>; >> + read-only; >> + }; >> + >> + developer-switch { >> + label = "developer-switch"; >> + gpios = <&gpx1 3 GPIO_ACTIVE_HIGH>; >> + read-only; >> + }; >> + >> + recovery-switch { >> + label = "recovery-switch"; >> + gpios = <&gpx0 7 GPIO_ACTIVE_LOW>; >> + read-only; >> + }; >> + }; >> + >> -- >> 2.1.4 >>
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