From: John Williams <john.williams@petalogix.com>
To: Linux Kernel list <linux-kernel@vger.kernel.org>
Cc: John Linn <John.Linn@xilinx.com>,
Stephen Neuendorffer <stephen.neuendorffer@xilinx.com>,
David DeBonis <david.debonis@xilinx.com>,
Michal Simek <michal.simek@petalogix.com>,
Grant Likely <grant.likely@secretlab.ca>
Subject: GPIOLIB, GPIO_SYS and port-wide accesses
Date: Fri, 14 Aug 2009 10:01:34 +1000 [thread overview]
Message-ID: <1d3f23370908131701w50f2c550r312b14b2c7f2d12c@mail.gmail.com> (raw)
Hi,
As I see it the gpiolib and sysfs export insists on single bit
accesses even on gpio pins that are located on the same physical
device/port.
A couple of years ago there was mention of port-wide accesses being a
good thing:
http://lkml.indiana.edu/hypermail/linux/kernel/0608.0/0731.html
(towards the bottom)
Did anything ever come of that?
Per-bit access is pretty inflexible if you are driving a 7-segment
display or 8-LED bar display, holding lots of file descriptors open
etc, and lots of syscall overhead.
sysfs syntax like
$ echo "240-247" > export
$ echo 255 > gpio240-247/direction (8-bit binary mask - output)
$ echo 255 > gpio240-247/value (all ones)
would be reasonably friendly, obviously the underlying gpiolib would
have to have some notion of coupled ports.
Any thoughts?
John
--
John Williams,
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com p: +61-7-30090663 f: +61-7-30090663
next reply other threads:[~2009-08-14 0:01 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-14 0:01 John Williams [this message]
2009-08-14 8:11 ` Ben Nizette
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