CAN stands for Controller Area Network, a broadcast network used
in automation and automotive fields. For example, the NMEA2000 standard
developped for marine devices uses a CAN network as the link layer.
This is an implementation of the linux socketcan API:
https://www.kernel.org/doc/Documentation/networking/can.txt
you can also see can(4).
This adds a new socket family (AF_CAN) and protocol (PF_CAN),
as well as the canconfig(8) utility, used to set timing parameter of
CAN hardware. Also inclued is a driver for the CAN controller
found in the allwinner A20 SoC (I tested it with an Olimex lime2 board,
connected with PIC18-based CAN devices).
There is also the canloop(4) pseudo-device, which allows to use
the socketcan API without CAN hardware.
At this time the CANFD part of the linux socketcan API is not implemented.
Error frames are not implemented either. But I could get the cansend and
canreceive utilities from the canutils package to build and run with minimal
changes. tcpudmp(8) can also be used to record frames, which can be
decoded with etherreal.
Unless the shell is compiled with the (compilation time) option
BOGUS_NOT_COMMAND (as in CFLAGS+=-DBOGUS_NOT_COMMAND) which it
will not normally be, the ! command (reserved word) will only
be permitted at the start of a pipeline (which includes the
degenerate pipeline with no '|'s in it of course - ie: a simple cmd)
and not in the middle of a pipeline sequence (no "cmd | ! cmd" nonsense.)
If the latter is really required, then "cmd | { ! cmd; }" works as
a standard equivalent.
In POSIX mode, permit only one ! ("! pipeline" is ok. "! ! pipeline" is not).
Again, if needed (and POSIX conformance is wanted) "! { ! pipeline; }"
works as an alternative - and is safer, some shells treat "! ! cmd" as
being identical to "cmd" (this one did until recently.)
It is possible to use a frequency of 44.1 kHz as apposed to 8 kHz if
you specifiy:
options HIRES_BELL
in your kernel config file.
Changes to the way in which the wave is generated help reducing pops and
ticks in the bell.
The output of the high resolution bell has been tested extensively using
frequency spectographs generated by pkgsrc package audio/audacity.
This addresses PR kern/51784.
inheritance when a variable is declared local, but instead leave
the local var unset (if not given a value) in the function.
Only ash derived shells do inheritance it seems.
So, to compensate for that, and get one step closer to making
"local" part of POSIX, so we can really rely upon it, a compromise
has been suggested, where "local x" is implementation defined
when it comes to this issue, and we add "local -I x" to specify
inheritance, and "local -N x" to specify "not" (something...)
(not inherited, or not set, or whatever you prefer to imagine!)
The option names took a lot of hunting to find something reasonable
that no shell (we know of) had already used for some other purpose...
The I was easy, but 'u' 'U' 'X' ... all in use somewhere.
This implements that (well, semi-) agreement.
While here, add "local -x" (which many other shells already have)
which causes the local variable to be made exported. Not a lot
of gain in that (since "export x" can always be done immediately
after "local x") but it is very cheap to add and allows more other
scripts to work with out shell.
Note that while 'local x="${x}"' always works to specify inheritance
(while making the shell work harder), "local x; unset x" does not
always work to specify the alternative, as some shells have
"re-interpreted" unset of a local variable to mean something that
would best be described as "unlocal" instead - ie: after the unset
you might be back with the variable from the outer scope, rather
than with an unset local variable.
Also add "unset -x" to allow unsetting a variable without removing
any exported status it has.
There are gazillions of other options that are not supported here!
fdtbus_get_reg will do a range check and return ERANGE if addr+size
exceeds 4GB.
Add fdtbus_get_reg64 to allow for fetching raw values w/o range check.
VOP_RECLAIM naturally has exclusive access to the vnode, so having it
locked on entry is not strictly necessary -- but it means if there
are any final operations that must be done on the vnode, such as
ffs_update, requiring exclusive access to it, we can now kassert that
the vnode is locked in those operations.
We can't just have the caller release the last lock because some file
systems don't use genfs_lock, and require the vnode to remain valid
for VOP_UNLOCK to work, notably unionfs.
Function names with cmp are expected to return the order of two comparees
like memcmp and strcmp. The functions in question just answer if matched
or not, so don't use cmp and use match instead.
Consistently return 1 on matched and 0 otherwise.
jmcneill