Re: [PATCH] ARM: dts: vf610-zii-dev-rev-b: add hi8435 device

From	Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] ARM: dts: vf610-zii-dev-rev-b: add hi8435 device
Date	2017-05-23 08:10 +0200
Message-ID	<tKbb4-7G0-9@gated-at.bofh.it> (permalink)
References	<tJVpD-6c9-9@gated-at.bofh.it> <tJYnw-80c-25@gated-at.bofh.it> <tJYnw-80c-33@gated-at.bofh.it> <tK0fD-HF-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

>> However, hi8435 driver historically was coded using inverted values
>> passed to gpiolib calls.  And there are setups in the wild with device
>> trees containing GPIO_ACTIVE_HIGH that I'd prefer not breaking.
>>
>> To solve, I submitted a patch on hi8435 driver that changes to _raw()
>> gpio calls (thus making it independent of what is written in device
>> tree), and want [future] device trees not to contain explicitly written
>> gpio polarity.
> 
> So maybe add another #define, GPIO_ACTIVE_IGNORED, to make it clear
> that it does not matter what value you put there, it is ignored.

"Crap origin" here is that in vast majority of cases, polarity is
per-chip, not per-chip-use, knowledge. And proper location for per-chip
knowledge is chip's driver.  Moving this knowledge to per-chip-use
location in device trees only provides a source for errors, with little
gain.

Vladimir Barinov mentions possibility that signal can be inverted by
board between gpio provider and chip's pin ...   but do we have at least
one practical case of this?  And if we even do, it's quite uncommon, and
something special should be required in device tree for these special
cases and not for "normal" cases.

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH] ARM: dts: vf610-zii-dev-rev-b: add hi8435 device Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-05-22 15:20 +0200
  Re: [PATCH] ARM: dts: vf610-zii-dev-rev-b: add hi8435 device Stefan Agner <stefan@agner.ch> - 2017-05-22 18:30 +0200
    Re: [PATCH] ARM: dts: vf610-zii-dev-rev-b: add hi8435 device Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-05-22 18:30 +0200
      Re: [PATCH] ARM: dts: vf610-zii-dev-rev-b: add hi8435 device Andrew Lunn <andrew@lunn.ch> - 2017-05-22 20:30 +0200
        Re: [PATCH] ARM: dts: vf610-zii-dev-rev-b: add hi8435 device Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-05-23 08:10 +0200

csiph-web