Introduce crossystem wrapper in SAFT.

Introduce crossystem wrapper for SAFT.

There has been an effort under way to abstract platform
specific information through the 'crossystem' utility, which
is capable of discovering information in platform specific
fashion and representing it in a unified way on all
platforms.

The BIOS ACPI on some platforms has been modified to support 
this, which of course broke SAFT completely.

This CL introduces a wrapper for crossystem to derive all
necessary information in a target independent way and
emulate information previously read directly from ACPI.

The actual SAFT fix will come in the next CL.

The 'crossystem' wrapper is a class which runs the
crossystem utility to retrieve or set the crossystem
parameters..

The __getattr__() method override is used to get the
value of an arbitrary crossystem parameter, so that
crossystem.name causes the shell command 

'crossystem name'

invocation to retrieve the value of parameter 'name'.

The __setattr__() method override is used to set the
crossystem parameters, such that assigning

crossystem.name = value

causes a shell command 

'crossystem "name=value"'

to be invoked. The only name not passed to the shell
command, but set directly is 'cros_if',  which is a
member of the crossystem wrapper class.


Change-Id: I59b547d899598501185a443cf2cffcc00330b37c

BUG=chrome-os-partner:2617
TEST=on the workstation:

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
es^o: home/vbendeb/projects/1repo/src/platform/saft 119 > ./runtests.sh 
....
----------------------------------------------------------------------
Ran 4 tests in 0.032s

OK
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=c034073

[vb, 2011-04-18 17:59:39]

On 2011/04/15 21:53:49, vb wrote:

Randal, as per our face to face discussion, I changed this not to cache
crossystem output, but to retrieve each parameter separately.

The tests still pass, please have another look.

[Randall Spangler, 2011-04-18 20:42:54]

LGTM

http://codereview.chromium.org/6849042/diff/9002/chromeos_interface.py
File chromeos_interface.py (right):

http://codereview.chromium.org/6849042/diff/9002/chromeos_interface.py#newcode34
chromeos_interface.py:34: return self.cros_if.run_shell_command_get_output(
What happens if crossystem exits non-zero (for example, if you access a
non-existent attribute)?

[vb, 2011-04-18 20:50:43]

On Mon, Apr 18, 2011 at 1:42 PM,  <rspangler@chromium.org> wrote:
> LGTM
>
>
> http://codereview.chromium.org/6849042/diff/9002/chromeos_interface.py
> File chromeos_interface.py (right):
>
>
http://codereview.chromium.org/6849042/diff/9002/chromeos_interface.py#newcode34
> chromeos_interface.py:34: return
> self.cros_if.run_shell_command_get_output(
> What happens if crossystem exits non-zero (for example, if you access a
> non-existent attribute)?
>

An exception is raised in case the shell command returns nonzero
value. I will add a test case for this in the upcoming CL (which
restores SAFT functionality).

cheers,
/v
> http://codereview.chromium.org/6849042/
>



-- 
Vadim Bendebury (mailto:vbendeb@google.com)
Google ChromeOS - (650) 253-7486