linux-kernel - Labelling GPIOs for sysfs access?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <56CF6844.2070802@vrt.com.au>
Date:	Fri, 26 Feb 2016 06:47:00 +1000
From:	Stuart Longland <stuartl@....com.au>
To:	linux-kernel@...r.kernel.org
Subject: Labelling GPIOs for sysfs access?

Hi all,

I've been porting the mainline Linux kernel to the Technologic Systems
TS-7670 industrial computers which are based on the Freescale i.MX286 SoC.

I've had to make a couple of hacks to get things working, my code is at
https://github.com/vrtsystems/linux/tree/ts7670-4.4.1

Right now, there's a couple of GPIO lines for controlling power to
things like RS-232 and CANBus transceivers.  The RS-485 port on these
devices also has a couple of pins that are connected to a CPU-controlled
MOSFET to allow turning an external device on/off.

Previously I used the generic GPIO sysfs interface.  This worked well,
but the names suddenly changed on me and so now my scripts don't work.
It's also not that user friendly.

Implementing a kernel driver is doable, but all I'm doing is just
repeating work that the sysfs GPIO interface does already.  Currently
I'm doing it with the "LEDs" framework, since they'll have a consistent
name -- users can for example, turn the RS-232 transceivers off by
setting /sys/class/leds/rs232_en/brightness to 0.  It's controlled by
device tree.

(Better in the case of RS-232, would be to have the port automatically
turn the transceivers on.  I managed to get the CANBus side to do that.)

Is there some sort of mechanism by which GPIO lines could be clearly
labelled to present a consistent interface in sysfs between kernel
revisions?

Regards,
-- 
     _ ___             Stuart Longland - Systems Engineer
\  /|_) |                           T: +61 7 3535 9619
 \/ | \ |     38b Douglas Street    F: +61 7 3535 9699
   SYSTEMS    Milton QLD 4064       http://www.vrt.com.au