Puppy Linux Discussion Forum

[technosaurus]

kernel's shell example (~16.0 seconds)

[technosaurus]

Next up: handling hotplug events

Process to figure out what to do:
1) need to know environment variables and args that are passed
--->use env >>somefile in a dummy script
--->echo /root/dummy /proc/sys/kernel/hotplug
2)use this data to analyze what we may need to do.

attaching a gzip output from removing then reinserting a usb flash drive

[Karl Godt]

Very nice as function for rc.sysinit !

time dyn_mknod

[technosaurus]

there is no need to prepend busybox ... (if busybox has it ash will use it)
and ERR-... should be ERR=... (probably the error source)
and what was the point of adding the rm ... ?
its usually better to use [ ! -f "$VAR" ] && command "$VAR"
... as it is, your rework will remove all existing nodes that are found and not recreate it (bad when Puppy uses a static /dev), but rerunning mknod on an existing device is quick and fails harmlessly (thus the 2>/dev/null)
keep in mind this script should only run once, so there shouldn't be any preexisting nodes (aside from the static ones that could be wrong)
also unnecessary echoes in loops really slow down scripts and should only be used for debugging - you can use OUTPUT="$OUTPUT
$NEWDATA" in the loop and then echo $OUTPUT afterwards

but Puppy's busybox is pretty conservatively built, if you're building it for an initrd, the following should be enabled 1)prefer applets, 2)standalone shell and 3)run nofork applets directly
This alone makes a 5x speed improvement.

Another related tip
"$VAR1/$VAR2" makes the whole thing one string because all variables are expanded inside double quotes (but not in single quotes) - using "$A"/"$B" is unnecessary and just slows it down

FYI - this makes it possible to construct a large command with many arguments (including quoted ones) - especially useful with programs like dialog Xdialog

[Karl Godt]

[technosaurus]

start of a hotplug script:

[Karl Godt]

For bsg device node path I could only think of reading the uevent files
like :

[technosaurus]

I used the uevent files in one of my jwm tools, but all you have to do is
. pathto/uevent
and it will source the variables in it

find will recurse the giant barrage of symlinks many levels, plus find is external, so if the path can be narrowed down to:

/sys/something/something/*/whatever
you can use a

[Karl Godt]

Don't know .. had to read https://en.wikipedia.org/wiki/Device_file

What seems to be that there are some doublettes there for both

Character devices:
1 mem
128 ptm
254 bsg


Block devices:
1 ramdisk
128 sd
254 mdp

[Karl Godt]

[technosaurus]

the while read blocks like that will skip the last line unless you do something like
while read LINE || [ "$LINE" ];do

guess we've been lucky the last thing is not important

in this case the LINE is a uevent file with shell formatted contents that can be sourced as a file with variable names, (but we may need to NULL out previous VARs if it is found that some uevent files do not contain all of MAJOR, MINOR, DEVNAME and DEVTYPE) such as:

[technosaurus]

here is my rework using /sys/dev/{char,block}/*/uevent

[technosaurus]

I uncovered a bug ... mknod will only accept major and minor 0..255, but the kernel supports higher values, so the mknod in busybox fails on /dev/bus/usb/004/001 (amongst others) because it has a minor value of 384 ... so I patched busybox mknod to use MINOR&0xff making it have an actual minor value of 128 - IDK if this is OK or not - probably not

musl-libc doesn't account for it, but it looks like uclibc and glibc do (prepends the extra bit in an unsigned int vs using just an unsigned short) - posting to musl-libc list

[Karl Godt]

The idea of sourceing is really fine !
Would probably come to it after several years due to not using eval gtkdialog or source /etc/rc.d/PUPSTATE much .
Most sourced files are actualy scripts containing functions .

*
Just did a
BusyBox v1.16.2 (2010-06-19 18:02:46 GMT-8 ) multi-call binary.
# busybox mknod /dev/test c 499 499
# ls -l /dev/test
crw-r--r-- 1 root root 499, 499 2013-05-13 17:12 /dev/test
# busybox mknod /dev/testb b 500 500
# ls -l /dev/testb
brw-r--r-- 1 root root 500, 500 2013-05-13 17:15 /dev/testb

seems to work OK.

[technosaurus]

I figured out a way to allow other packages to provide their own configurations for a shell script. this one is an example for a hotplugger shell script replacement (just the subsystem section)