From: Andrew Jeffery <andrew@aj.id.au>
To: Joel Stanley <joel@jms.id.au>
Cc: Patrick Williams <patrick@stwcx.xyz>, OpenBMC <openbmc@lists.ozlabs.org>
Subject: Re: GPIO offsets used by userspace
Date: Tue, 31 Jan 2017 11:45:12 +1030 [thread overview]
Message-ID: <1485825312.4137.25.camel@aj.id.au> (raw)
In-Reply-To: <CACPK8XeOQPONhwQ4Q6bPUp7=-AoFArXwCmzDC-tors00i_u=tg@mail.gmail.com>
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On Tue, 2017-01-31 at 10:55 +1030, Joel Stanley wrote:
> > On Mon, Jan 30, 2017 at 12:04 PM, Andrew Jeffery <andrew@aj.id.au> wrote:
> > Hi all,
> >
> > Just a heads up that when the linked patch is pulled into the OpenBMC
> > kernel it will break our userspace. We will need to synchronise the
> > kernel bump with the fixes for the machine configs to update the magic
> > GPIO offset number.
> >
> > https://lkml.org/lkml/2017/1/26/786
> >
> > The magic offset is essentially 512-(ngpios) (I don't know why, but
> > that's the behaviour), and this now varies between AST2400 and AST2500
> > systems due to the AST2500 having an extra bank, and also because the
> > AST2400 has a "hole" at the end of its GPIO number space.
>
> Can you suggest a way to detect this from userspace?
Not off the top of my head.
>
> Would using the chardev api make this easier?
To a degree. I'm not sure if named gpios are exposed by the sysfs
interface, but with the chardev API you can open the devices and
request a GPIO by name. If that fails and you have multiple devices, I
guess you can try the other gpiochips.
Andrew
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next prev parent reply other threads:[~2017-01-31 1:15 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-30 1:34 GPIO offsets used by userspace Andrew Jeffery
2017-01-31 0:25 ` Joel Stanley
2017-01-31 0:50 ` Hergert, Nolan
2017-01-31 1:12 ` Andrew Jeffery
2017-01-31 1:23 ` Hergert, Nolan
2017-01-31 18:06 ` Patrick Williams
2017-01-31 1:15 ` Andrew Jeffery [this message]
2017-01-31 22:15 ` Xo Wang
2017-01-31 23:25 ` Joel Stanley
2017-02-01 1:26 ` Xo Wang
2017-02-01 2:20 ` Andrew Jeffery
2017-02-07 1:41 ` Andrew Jeffery
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