Using ext4 usb drive to go to 13.1.0

[James Cameron]

G'day Bruno,

Thank you for your problem report.  It is interesting.

The install method hasn't changed.  Our development builds are
installed using fs-update rather than the zsp file and holding four
game keys down.  Once 13.1.0 is released, the method will be the same
as before.

None of my USB drives show a problem, so the cause may be both USB
drive and Open Firmware in combination.  I'd like to fix this, because
I've been told that every type of USB drive must work.  So I'll need
to work with your USB drive over e-mail or IRC.

When you upgraded your XO-1.75 to 12.1.0 an old version of Open
Firmware might have been present.  After the upgrade, the next time
you had two sources of power, Open Firmware would have been upgraded.

This might explain why you saw a different result.  Open Firmware has
had hundreds of changes between those two versions, some of which may
have contributed to the problem you report.  Many of them relate to
USB, and many of them were mine.

To find which changes are important, here is what I need:

a.  what version of Open Firmware was on the XO-1.75 before the
upgrade to 12.1.0?  I cannot guess what this was.

b.  what version of Open Firmware was on the XO-1.75 at the time of
the problem in ticket #12123?  I expect it was Q4D17 as this was
12.1.0 build 21 contained.

c.  what version of Open Firmware is on the XO-1.75 after the upgrade
to 13.1.0?  I expect it will be Q4D21.

d.  if you downgrade to the version of Open Firmware you had before
the upgrade to 12.1.0, and then try the fs-update for 13.1.0, does the
problem in ticket #12123 occur?

e.  on Q4D21 please attach the USB drive, turn on the laptop,
get to the ok prompt, type p2, and tell me what is printed.

f.  on Q4D21 please detach the USB drive, turn on the laptop, get to
the ok prompt, type p2, and tell me what is printed.

g.  on Q4D21 please attach the USB drive, turn on the laptop, get to
the ok prompt, type

	ok " /" ['] (show-usb2) scan-subtree

and tell me what is printed.  This lists the devices without probing
again.

I may have other questions once I have these answers.


Some technical background to help you diagnose the situation further.
For fs-update to work correctly, the following must occur:

0. the laptop must turn on the USB power,

1. the drive must power up,

2. the drive must spin up and become ready (if it is a mechanical
drive this can take some seconds),

3. the drive must respond to a USB probe,

4. the partition table must be read,

5. the filesystem must be read,

6. the directory, if any, must be read,

7. the file must exist in the directory with the specified name,

8. the data blocks of the file must be read.

You said that it worked fine if the drive was plugged in after the ok
prompt appeared, but not if the drive was plugged in before.  So I'd
like to focus on steps 1 to 3 first, to make sure they are working
correctly.

Open Firmware has a command for probing USB devices.  It is probe-usb
which can be abbreviated to p2.  Thus:

	ok p2

At the end of the probe, it lists all USB devices detected since power
up.

Open Firmware also does a probe-usb during startup, very soon after
USB power is turned on.  If the drive takes too long to start, it
might not respond to this probe.  (A few changes we made cause Open
Firmware to start more quickly.)

You can list all USB devices detected since power up, without doing a
probe, by typing this command:

	ok " /" ['] (show-usb2) scan-subtree

The command above is what probe-usb does after the probe and before
showing the ok prompt.

The probe list is also helpful for another reason ... if a drive does
not appear in this list, it cannot be mounted, because the probe has
not been successful.  However, a drive that cannot be mounted may
appear in this list, because there may be another reason for the
failure.

Lastly, correcting a terminology issue ... there is no Open Firmware
command to see what drives are mounted, because drives are not mounted
until they are used, then when the command completes they are
unmounted.  But you can ask for a list of files, and this checks steps
4, 5 & 6.

	ok dir u:

-- 
James Cameron
http://quozl.linux.org.au/