I limited potentially infinite timings by 960 us based on a footnote on
page 38 of Maxim Integrated Application Note 937, Book of iButton
Standards: "In order not to mask interrupt signalling by other devices
on the 1–Wire bus, tRSTL + tR should always be less than 960 us."
MFC after: 3 weeks
Previously we used the minimal value of 1 us and it was really tight.
Application Note 3829 has a table describing recommended t_rec values
for various bus voltages, temperature conditions and numbers of slave
devices. The new value decreases the maximum possible data rate from
16.3 Kbit/s to 13.3 Kbit/s, but it allows for up to four slaves on a
3.3V bus (under room temperature).
References:
- Maxim Integrated Application Note 3829
Determining the Recovery Time for Multiple-Slave 1-Wire(R) Networks
- Maxim Integrated Application Note 937
Book of iButton Standards
Discussed with: imp (D22108)
MFC after: 3 weeks
Previously the code used sbttous() before microseconds comparison in one
place, sbttons() and nanoseconds in another, division by SBT_1US and
microseconds in yet another.
Now the code consistently uses multiplication by SBT_1US to convert
microseconds to sbintime_t before comparing them with periods between
calls to sbinuptime(). This is fast, this is precise enough (below
0.03%) and the periods defined by the protocol cannot overflow.
Reviewed by: imp (D22108)
MFC after: 2 weeks
The lock is used only for start / stop signaling.
It is used only for 'flags' field and the related condition variable.
This change is a follow-up to r354067, it was suggested by Warner in
D22107.
Suggested by: imp
MFC after: 1 week
This is similar to what is done around other calls that lead to
own_command_wait() that can sleep.
Reviewed by: imp
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D22107
"fdt" is removed from the driver module name as the driver does not
require FDT and can work very well on hints based systems.
A module dependency is added for gpiobus. Without that owc cannot
resolve symbols in gpiobus if both are loaded as kernel modules.
Finally, a driver module module version is added.
Reviewed by: imp
MFC after: 11 days
This allows replacing "sys/eventfilter.h" includes with "sys/_eventfilter.h"
in other header files (e.g., sys/{bus,conf,cpu}.h) and reduces header
pollution substantially.
EVENTHANDLER_DECLARE and EVENTHANDLER_LIST_DECLAREs were moved out of .c
files into appropriate headers (e.g., sys/proc.h, powernv/opal.h).
As a side effect of reduced header pollution, many .c files and headers no
longer contain needed definitions. The remainder of the patch addresses
adding appropriate includes to fix those files.
LOCK_DEBUG and LOCK_FILE_LINE_ARG are moved to sys/_lock.h, as required by
sys/mutex.h since r326106 (but silently protected by header pollution prior
to this change).
No functional change (intended). Of course, any out of tree modules that
relied on header pollution for sys/eventhandler.h, sys/lock.h, or
sys/mutex.h inclusion need to be fixed. __FreeBSD_version has been bumped.
OF_finddevices returns ((phandle_t)-1) in case of failure. Some code
in existing drivers checked return value to be equal to 0 or
less/equal to 0 which is also wrong because phandle_t is unsigned
type. Most of these checks were for negative cases that were never
triggered so trhere was no impact on functionality.
Reviewed by: nwhitehorn
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D14645
Use them in some existing code that is vulnerable to roundoff errors.
The existing constant SBT_1NS is a honeypot, luring unsuspecting folks into
writing code such as long_timeout_ns*SBT_1NS to generate the argument for a
sleep call. The actual value of 1ns in sbt units is ~4.3, leading to a
large roundoff error giving a shorter sleep than expected when multiplying
by the trucated value of 4 in SBT_1NS. (The evil honeypot aspect becomes
clear after you waste a whole day figuring out why your sleeps return early.)
Coverity reports an uninitialized "dir" in case the switch defaults
without hitting any case. Respect the original intent and quell the
false positive with the relatively new __unreachable() builtin.
CID: 1331566
only gpiobus configured via FDT is supported. Bus enumeration is
supported. Devices are created for each device found. 1-Wire
temperature controllers are supported, but other drivers could be
written. Temperatures are polled and reported via a sysctl. Errors
are reported via sysctl counters. Mis-wired bus detection is included
for more trouble shooting. See ow(4), owc(4) and ow_temp(4) for
details of what's supported and known issues.
This has been tested on Raspberry Pi-B, Pi2 and Beagle Bone Black
with up to 7 devices.
Differential Revision: https://reviews.freebsd.org/D2956
Relnotes: yes
MFC after: 2 weeks
Reviewed by: loos@ (with many insightful comments)
