Npf's blog

Playing with old Linux embedded devices is not easy: First of all, old devices get forgotten and are not supported by new versions of software (e.g. kernel) once they are not the subject of concern of a critical mass of people. No long term support for hobbyist goodies... But worse than that, web sites or package repositories which are dedicated to those devices happen to vanish... I have to say it the case for several devices I own:

• My Ipaq used to be the first hand-held device (PDA) supported by Linux (2001), but today there are few hopes to get the bits that made it working.
• My N900 has no more available Debian repositories...
• My Beagleboard has some interesting web sites that became dead ends.

Lets talk more about my Beagleboard (I might talk about my N900 in a future post). Hopefully, if some web pages (e.g. at angstrom linux) are dead, that are still a good support for the devices:

The following pages are the references for the Beagleboard. They are still the source of many information, but have more and more dead links:

• http://beagleboard.org/latest-image...
• http://elinux.org/Beagleboard:Beagl...
• http://elinux.org/BeagleBoard_Commu...
• http://elinux.org/BeagleBoardDebian
• http://elinux.org/BeagleBoardNAND
• http://elinux.org/BeagleBoardBeginn...

The following google code pages are mostly outdated with dead links to some Angstrom Linux web pages. Anyway, they might still prove useful:

• https://code.google.com/p/beagleboa...
• https://code.google.com/p/beagleboa...
• https://code.google.com/p/beagleboa...
• https://code.google.com/p/beagleboa...
• https://code.google.com/p/beagleboa...
• https://code.google.com/p/beagleboa...
• http://angstrom.s3.amazonaws.com/de...
• http://feeds.angstrom-distribution....
• http://dominion.thruhere.net/angstr...

But hopefully, everything is there in the following pages to get even an old Beagleboard (rev c3) up and running with a recent kernel and a fresh Debian!:

• https://github.com/beagleboard
• https://github.com/RobertCNelson/fl...
• https://github.com/RobertCNelson/ne...
• https://github.com/RobertCNelson/om...

Also some useful links regarding Nand and ubifs:

• http://free-electrons.com/blog/crea...
• http://www.linux-mtd.infradead.org/...
• http://processors.wiki.ti.com/index...
• http://processors.wiki.ti.com/index...
• http://processors.wiki.ti.com/index...

And now some rough notes of my testings:

mmc rescan
fatload mmc 0:1 ${loadaddr} uimage--3.14.25-r0.2-beagleboard-20150302185947.bin

ext4ls mmc 0:2 /home/root
ext4load mmc 0:2 ${loadaddr} /home/root/uImage-beagleboard.bin

ext2load mmc 0:2 ${loadaddr} /home/root/uImage-beagleboard.bin

ext4load mmc 0:2 ${loadaddr} /home/root/base-image-beagleboard.ubi
nandecc
mtdparts default
nand erase.part fs
nand write ${loadaddr} fs


nand read ${loadaddr} kernel

bootm start ${loadaddr}

---
U-Boot# ext4load mmc 0:2 ${loadaddr} /home/root/uImage-beagleboard.bin
4274232 bytes read in 349 ms (11.7 MiB/s)
U-Boot# bootm start ${loadaddr}
## Booting kernel from Legacy Image at 82000000 ...
   Image Name:   Linux-3.14.25
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    4274168 Bytes = 4.1 MiB
   Load Address: 80008000
   Entry Point:  80008000
   Verifying Checksum ... OK
---

mtdparts
mtdparts default
setenv nandroot 'ubi0:rootfs ubi.mtd=4,2048'
run nandargs
bootm

* Angstrom linux cmdline:
console=tty0 mpurate=auto buddy=unknown buddy2=unknown camera=none vram=12M omapfb.mode=dvi:640x480MR-16@60 omapdss.def_disp=dvi root=/dev/mmcblk0p2 ro rootfstype=ext3 rootwait


root@beagleboard:~# flash_eraseall /dev/mtd4
flash_eraseall has been replaced by `flash_erase <mtddev> 0 0`; please use it
Erasing 128 Kibyte @ 4040000 -- 25 % complete flash_erase: Skipping bad block at 04060000
Erasing 128 Kibyte @ f960000 -- 100 % complete 
root@beagleboard:~# ubiformat /dev/mtd4
mtd4    mtd4ro  

root@beagleboard:~# ubiformat /dev/mtd4 -s 512 -O 512
ubiformat: mtd4 (nand), size 261619712 bytes (249.5 MiB), 1996 eraseblocks of 131072 bytes (128.0 KiB), min. I/O size 2048 bytes
libscan: scanning eraseblock 1995 -- 100 % complete  
ubiformat: 1995 eraseblocks are supposedly empty
ubiformat: 1 bad eraseblocks found, numbers: 515
ubiformat: formatting eraseblock 1995 -- 100 % complete  
root@beagleboard:~# modprobe ubi   
root@beagleboard:~# modprobe ubifs
root@beagleboard:~# ubi
ubiattach     ubiformat     ubinize       ubirsvol      
ubicrc32      ubimkvol      ubirename     ubiupdatevol  
ubidetach     ubinfo        ubirmvol      

root@beagleboard:~# ubiattach /dev/ubi_ctrl -m 4 
[  310.406860] UBI: attaching mtd4 to ubi0
[  310.410919] UBI: physical eraseblock size:   131072 bytes (128 KiB)
[  310.417633] UBI: logical eraseblock size:    129024 bytes
[  310.423553] UBI: smallest flash I/O unit:    2048
[  310.428588] UBI: sub-page size:              512
[  310.433410] UBI: VID header offset:          512 (aligned 512)
[  310.439605] UBI: data offset:                2048
[  310.940551] UBI: max. sequence number:       0
[  310.962921] UBI: attached mtd4 to ubi0
[  310.966857] UBI: MTD device name:            "File System"
[  310.972747] UBI: MTD device size:            249 MiB
[  310.978240] UBI: number of good PEBs:        1995
[  310.983245] UBI: number of bad PEBs:         1
[  310.987915] UBI: number of corrupted PEBs:   0
[  310.992645] UBI: max. allowed volumes:       128
[  310.997467] UBI: wear-leveling threshold:    4096
[  311.002471] UBI: number of internal volumes: 1
[  311.007202] UBI: number of user volumes:     0
[  311.011840] UBI: available PEBs:             1972
[  311.016845] UBI: total number of reserved PEBs: 23
[  311.021850] UBI: number of PEBs reserved for bad PEB handling: 19
[  311.028320] UBI: max/mean erase counter: 0/0
[  311.032836] UBI: image sequence number:  1860044559
[  311.038085] UBI: background thread "ubi_bgt0d" started, PID 531
UBI device number 0, total 1995 LEBs (257402880 bytes, 245.5 MiB), available 1972 LEBs (254435328 bytes, 242.6 MiB), LEB size 129024 bytes (126.0 KiB)

root@beagleboard:~# ubimkvol /dev/ubi0 -N rootfs -m
Set volume size to 254435328
Volume ID 0, size 1972 LEBs (254435328 bytes, 242.6 MiB), LEB size 129024 bytes (126.0 KiB), dynamic, name "rootfs", alignment 1
root@beagleboard:~# mount -t ubifs ubi0:rootfs /mnt/
[  421.361236] UBIFS: default file-system created
[  421.422698] UBIFS: mounted UBI device 0, volume 0, name "rootfs"
[  421.429168] UBIFS: file system size:   252887040 bytes (246960 KiB, 241 MiB, 1960 LEBs)
[  421.437835] UBIFS: journal size:       12644352 bytes (12348 KiB, 12 MiB, 98 LEBs)
[  421.445831] UBIFS: media format:       w4/r0 (latest is w4/r0)
[  421.452026] UBIFS: default compressor: lzo
[  421.456329] UBIFS: reserved for root:  4952683 bytes (4836 KiB)


root@beagleboard:/mnt# xzcat /home/root/base-image-beagleboard.tar.xz | tar x^C
root@beagleboard:~# df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/root                 3.3G    599.8M      2.5G  19% /
devtmpfs                113.1M         0    113.1M   0% /dev
tmpfs                   113.2M         0    113.2M   0% /dev/shm
tmpfs                   113.2M    316.0K    112.9M   0% /run
tmpfs                   113.2M         0    113.2M   0% /sys/fs/cgroup
tmpfs                   113.2M    316.0K    112.9M   0% /var/run
tmpfs                   113.2M    316.0K    112.9M   0% /var/lock
tmpfs                   113.2M         0    113.2M   0% /media
tmpfs                   113.2M      4.0K    113.2M   0% /tmp
ubi0:rootfs             226.1M     38.2M    183.3M  17% /mnt

Enigma of the day:

(click to see full size)

Answer wanted as GNU/Linux commands...

(download the drawing sources)

Forewords:

Once again today, I had to rollback the master branch of a remote Git repository to a previous state in a history. I mean deleting the last commits of the branch (not undoing them), so that they just do not appear neither in the content of the repository nor in the history of the branch.

Yes, this is very bad, but it's doable . Just mind the fact that anyone who might have pulled into his local repository a state in between the current state and the state we want to revert to (excluded), will have to clone again the repository.

Do the trick

Send a mail

First of all, we send a mail to the other developers, so that they do not pull changes until you give them a go. Also you might inform them that they might receive a bunch of mails if they are subscribed to a commit notification mailing list due to our operations to come.

Delete the local master branch and watch your back

It's always good to take some guarantees when doing dirty things... In our case, the first thing is to backup a pointer to the current state of the branch, before deleting the branch. We actually do it by renaming the master branch instead of deleting it.

$ git checkout master
$ git branch -m master master.orig

Change origin's default branch

To be able to delete the master branch, it must not be the remote repository HEAD aka default branch. It often is however, so we first need to change that.

Before trying to change it, we need to make sure there is at least one other branch on the remote repository (otherwise, to what branch change the HEAD ?). We can push master.orig to origin for instance. We'll delete it once finished with the master one.

On GitHub, changing the default branch is just the matter of finding the good administration page: we go to the setting page, and the default branch combo-box input shows up. Switch to something else than master.

On a Git repository hosted on a server that we can ssh to, we can change the default branch (HEAD) by going to the repository's directory, and then use the git symbolic-ref command:

$ ssh git_server
git_server$ cd /path/to/the/directory/of/the/git/repository/ 
git_server$ git symbolic-ref HEAD
refs/heads/master
git_server$ git symbolic-ref HEAD refs/heads/master.orig

NB: We could also just modify the HEAD file in a bare repository, looks like it achieves the same goal.

Delete origin/master

Deleting the remote master branch is now just the matter of knowing the command... It uses to be:

$ git push origin :master

But actually, there is now quite an explicit command:

$ git push origin --delete master

Create the new local master branch

First of all we need to pick a commit hash reference, copy-pasting it from git log for instance. Then we check-out/create the branch:

$ git checkout 6fb1f9a16fd73bd0bdbf6defdb755186fa38a980 -b master

Push the new master branch to origin

As usual:

$ git push origin master

Clean-up our mess

We can now reset the default branch (HEAD) on origin, using the same method as above.

Then we can delete our backup temporary branches:

$ git branch -d master.orig
$ git push orig --delete master.orig

We are done !

Forewords

Its been a long time since I started being a Enlightenment addict (year 2000 I think). And although I never moved to E17, I'm pretty happy to yet see new releases for the version I love: E16.

Indeed, E16 is still packaged in my favorite distro (Debian), is well integrated with Gnome (and is a excellent replacement for the very basic metacity). E16 even gets updates !

Today, I discovered the compiste mode or E16 ! which comes with a real opacity feature

So what ? What can opacity bring of so much interest ? That's a really good question.

Indeed, speaking about cool window managers, I actually care about the efficiency one gives to me. So I'd agree with people promoting the self organizing one, doing auto tiling for instance (dwm, ion, xmonad for instance). However, I never really used one of them. Indeed I like to see my computer desktop organized just like my real desktop: stuffs laying everywhere, overlapping the one over the others but looked for and found in only the wink of an eye. E16 pager managing multiple areas is just the feature I was so happy to find years ago, and I couldn't loose, giving my the global picture of my never-mess .

So what ? Opacity ? It's nice yes, but how is it really useful in my context ?

Today, my office-mate told me a truth: yes being able thanks to the opacity/transparency to see windows laying around under another can be useful to keep an eye on what's behind. No more Alt+Tab cycling of windows to find just one hidden below another. But imagine a program execution you're watching though the transparency of you front-most window and that you should suddenly absolutely stop, as an emergency ! Yeah Alt+Tab or the like allows you to raise a window, but what if there is plenty of them in the current area ! You end up raising windows the one after the others, and in the panic, you just miss the one ! So what ? Cycle again ?

Here is the truth of my friend: you need a way to instantly raise the window you see under your mouse pointer though the transparency of your current window !. If you do that I owe you a beer . Badly no window manager he knew so far provides that... even E16.

No way. E16 can do it, thanks to its IPC feature. Eesh enters the play.

End of blabla, follows things you need to customize E16 to play nice with opacity,

Making it work

Obviously before anything please check that your hardware and X server provide the X11 composite extension (need a quite recent hardware). If not, hit the road jack... Then activate the composite mode in E16 setting, and set the opacity the the value you wish (obiously non 100% neither for the focused windows, nor the others). You're then all set for the following.

NB:

• Please note that I use MOD4 as my favorite windows modifier/function key, which actually maps to the Windows key of my keyboard.
• Also make sure you have your own version of the bindings.cfg configuration file in your ~/.e16/ by copying /etc/e16/bindings.cfg.

Part 1: raising windows laying below others under the mouse pointer

Part 1.1: cycle though the stack of window laying under your pointer

This one is pretty straigh forward... Too bad I started by solving the 1.2 problem .

just add the following keybindings to your E16 setup by editing the ~/.e16/bindings.cfg config file and adding to the Aclass KEYBINDINGS global section the following line:

KeyDown    4      Tab wop * lower

then just restart E16

eesh restart

Hitting MOD4+Tab now will cycle the windows under your pointer, but only those ones, to the contrary of Alt+Tab that cycle all windows of the area.

Problem: once I've hit MOD4+Tab, how do I get my lowered window back to front (assuming I have more than 2 windows below my pointer)... argh !

Part 1.2: no I just want to swap the top 2 of 3 (or N) windows under the pointer

This part is covered by the script I actually wrote initially, before I found out that 1.1 already provided almost what I wanted. But not all what I wanted, ouf I did not loose my time .

We need a script to list the stack of windows under the pointer, then we need to raise one of then, the 2nd, the 3rd or the Nth in the stack, our choice. I put this script in the file /home/npf/bin/e-zpick.sh (you can of course change the pathname as you like).

cat <<'EOF' > /home/npf/bin/e-zpick.sh
#!/bin/bash

Z=${1:-1}
POS=$(eesh "warp ?")
POS_XY=${POS#*: }
POS_X=${POS_XY% *}
POS_Y=${POS_XY#* }

for L in $(eesh "wl all" | tr " " "_" ); do
	T=${L:1:9}
	WIN_ID=${T##*_}
	T=${L:13:5}
	WIN_X=${T##*_}
	T=${L:19:5}
	WIN_Y=${T##*_}
	T=${L:25:4}
	WIN_W=${T##*_}
	T=${L:30:4}
	WIN_H=${T##*_}
	if [ $POS_X -ge $WIN_X -a $POS_X -le $((WIN_X + WIN_W)) -a $POS_Y -ge $WIN_Y -a $POS_Y -le $((WIN_Y + WIN_H)) ]; then
		echo $L
		WIN_ID_SEL[I++]=$WIN_ID
	fi
done
eesh "wop ${WIN_ID_SEL[Z]} focus"
EOF

Then we register the keybindings and mousebindings to use e-zpick.sh. Again edit the ~/.e16/bindings.cfg config file and adding to the Aclass KEYBINDINGS global section the following lines:

KeyDown    4        1 exec /home/npf/bin/e-zpick.sh 1
KeyDown    4        2 exec /home/npf/bin/e-zpick.sh 2
KeyDown    4        3 exec /home/npf/bin/e-zpick.sh 3
KeyDown    4        4 exec /home/npf/bin/e-zpick.sh 4

And to the Aclass BUTTONBINDINGS normal the following lines:

MouseDown      4 1 exec /home/npf/bin/e-zpick.sh 1
MouseDown      4 3 exec /home/npf/bin/e-zpick.sh 2

then just restart E16 again

eesh restart

Now:

• Hitting MOD4+1 or MOD4 and clicking on the left mouse button will cycle top window with the one below
• Hitting MOD4+2 or MOD4 and clicking on the right mouse button will cycle top window with the two below
• Hitting MOD4+3 cycle top window with the three below
• Hitting MOD4+4 cycle top window with the for below
• five ? no, really ? help yourself.

Part 2: quickly changing the opacity of a window when transparency is boring

We now made the opacity/transparency feature useful, but we however know that it will from time to time be very annoying Here are some additionnal binding to overcome this (we hope)...

First, we want to be able to disable/enable the transparency using a keystroke. We add to the Aclass KEYBINDINGS global section in ~/.e16/bindings.cfg:

KeyDown    4        q wop * focused_opacity 100
KeyDown    4        a wop * focused_opacity 0
KeyDown   A4        q wop * opacity 100
KeyDown   A4        a wop * opacity 0

Second we also add mouse binding for the same purpose. We add to the Aclass BUTTONBINDINGS normal section in ~/.e16/bindings.cfg:

MouseDown      4 2 wop * focused_opacity 100 
MouseDouble    4 2 wop * focused_opacity 0 
MouseDown     A4 2 wop * opacity 100 
MouseDouble   A4 2 wop * opacity 0 
MouseDown      4 4 wop * focused_opacity -10 
MouseDown      4 5 wop * focused_opacity +10 

Finally restart E16.

eesh restart

Now:

• Hitting MOD4+q or MOD4 and clicking on the mouse wheel will make the current window completely opaque when focused.
• Hitting MOD4+a or MOD4 and double-clicking on the mouse wheel will revert to the default focused opacity setup for the window.
• Hitting Alt+MOD4+q or Alt+MOD4 and clicking on the mouse wheel will make the current window completely opaque, when focused or not.
• Hitting Alt+MOD4+a or Alt+MOD4 and double-clicking on the mouse wheel will revert to the default opacity setup for the window (focused or not).
• Hitting MOD4 and rolling-up the mouse wheel will increase the opacity value from 0 (the default opacity) to 10%, and then up to 100%. Rolling-down of course do the reverse. (somebody told me MACOS X provides that... but that was no challenge )

Enjoy the beer .