Messages in this thread | | | From | Linus Walleij <> | Date | Thu, 16 Aug 2018 10:11:38 +0200 | Subject | Re: [PATCH] gpio: 74x164: add lines-initial-states property |
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Hi David,
On Wed, Aug 15, 2018 at 10:19 PM David Bauer <mail@david-bauer.net> wrote:
> This adds the ability to define the initial state of each output line on > device probe. > > Signed-off-by: David Bauer <mail@david-bauer.net>
(...) > Optional properties: > - enable-gpios: GPIO connected to the OE (Output Enable) pin. > +- lines-initial-states: Bitmask that specifies the initial state of > + each line. When a bit is set to zero, the corresponding output line > + is initialized LOW. When a bit is set to one, the corresponding > + output line is initialized HIGH. In case this property is not > + defined, all lines will be initialized as LOW.
This sounds like something that should be generic, and not use a bitmask, but offsets. It should work even if the number of GPIOs from the chip is > 32.
Is the usecase different from hogs? See Documentation/devicetree/bindings/gpio.txt
There has been extensive discussion about supporting initial values with something similar to hogs, but I haven't got anything ACKed by the DT maintainers so it has kind of stalled.
I would make sure to both make it generic, get ACK from the DT mainatiners, and make sure to implement it in drivers/gpio/gpiolib-of.c and not locally in drivers.
Yours, Linus Walleij
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