More LiveCD space optimizations

[Josua Dietze]

Martin Owens:
[quote]

On Fri, 2010-11-05 at 16:20 -0400, Martin Pitt wrote:
  > One thing that currently needs it is usb-modeswitch. I'd love the
  > usb-modeswitch-dispatcher thing to be rewritten in C, Vala, or another
  > compiled language. Not only is it holding tcl in the default install,
  > but it also dramatically slows down boot.

That already is written in C, it's the script that pulls in the config
and runs the usb_modeswitch program which is written in tcl.

It should be very possible to convert it to python or vala.

I have to wonder what 200 udev rules all with different vendor and
product ids does to the boot time.

[/quote]

Allow me to explain a few things, wrapping up from the end:

There is nothing that can be done about the udev rules. There are many 
different devices now that need a mode switch, each to be treated 
individually. And the rules are already filtered to only being looked at 
for subsystem "usb", action "add", and specific interfaces having device 
class 8. I assume you can't even measure a boot time difference with and 
without these rules.

What *can* be done is to avoid running the Tcl script if no such device is 
present. This is the state of things in the vast majority of cases, taken 
care of by the udev rules.
One special case of a reboot with an already switched device is fixed in 
the coming-up version 1.1.5 so that the Tcl wrapper is definitely only run 
when really needed (modem ID not yet covered by "option" module).
Given that the device switching itself takes around 5 to 20 seconds 
depending on the respective device firmware, the running time of the Tcl 
script is really negligible.

BTW, the "wrapper-wrapper" sh script will fork and never hold up the udev 
phase.

Regarding the wrapper mechanism itself it is important to note that there 
is a deliberate separation between the C code and the script. The C part is 
meant to be portable to non-Linux systems and only depends on libusb. The 
script does the main task of properly identifying devices, for which the 
USB IDs are just not sufficient (example: 05c6:1000).
It also enables new devices not known to the "option" driver yet to bind to 
it at runtime. Users of new models are able to use them with very small 
additions to the setup.

Now the Tcl language: I can see that it is hard to carry it on if there is 
only one system-related usage case. I will downright refuse to convert the 
wrapper into a binary for tranparency reasons, but I'm open to suggestions 
regarding other script languages that are expected to stay on the Live CD. 
Let me just say that I hate the Bash syntax, and I would use Perl only if 
held at gunpoint :-)

And on a grumbling side remark, the Tcl shell including the lib is 1.1 MB 
unpacked on my system. Oh well. I'm all for a Live *DVD*.

Josua Dietze