How to downgrade a jail-broken 5.6.1 kpw2?

[variousvirgil]

Hi, everyone!
I have a jailbroken kpw2 with firmware version 5.6.1, with RP installed, and I want to know how to downgrade it since the updater of 5.6.1 is really evil. THANKS!

[knc1]

Originally Posted by variousvirgil

Hi, everyone!
I have a jailbroken kpw2 with firmware version 5.6.1, with RP installed, and I want to know how to downgrade it since the updater of 5.6.1 is really evil. THANKS!

Step #1: Connect your 1.8v low-voltage serial to USB adapter to the Kindle operator's serial port ;

Step #2: If you get past #1, then there are several recent threads on the subject that include step-by-step.

[NiLuJe]

@variousvirgil: Which JB version did you have before the update?

[knc1]

Sorry, I missed that point, I must have been speed reading over the important facts again.

[variousvirgil]

Thanks for your reply.
@NiLuJe: I installed the bridge of 1.13 JB, and excuted JB script in kterm manually because the update bin doesn't work for 5.4.5.1, and the JB does work well in 5.6.1
@knc1: Can we use RP to downgrade?

[NiLuJe]

@variousvirgil: Why do people keep trying to install both the bridge and the JB? (That's not a rhetorical question, I'm quite keen to know what in the docs leads you to believe that's needed).

That said, yes, you can downgrade from diags, just get the kernel & rootfs from an official update w/ kindletool, and flash it manually. This thread details the procedure, albeit for a different device/FW version, but that's still relevant, just use the proper files.

Make *absolutely* sure you're using a FW version targeting your device, or you will shoot yourself in the foot.

[variousvirgil]

@NiLuJe: I have to admit this reflects some kind of anxiety, LOL
Anyway, thanks for your hospitable and effective help!

[variousvirgil]

I forgot to ask whether the "seek" argument in dd command is still 65.

[NiLuJe]

Excellent question to which I'm not sure I have the answer, sorry .

[knc1]

Originally Posted by variousvirgil

I forgot to ask whether the "seek" argument in dd command is still 65.

Do you mean in step #8?
Install the 5.3.0 main kernel: dd if=/mnt/us/uImage of=/dev/mmcblk0 bs=4096 seek=65

The 'seek' argument skips obs (output blocks) before it starts writing.

Which means that /dev/mmcblk0 would have to (still) be laid out on your device the same as it was on the device for which the directions where written.

Now that you can confirm for your device:
1) copy some small number of blocks (say 100) to your pc -
dd if=/dev/mmcblk0 of=your_choice bs=4096 count=100

2) use your favorite hex dumper (od is a good choice) to copy some small 'signature' string from
uImage.
The format of a uImage file hasn't change in a long time - the first 16 bytes will probably get enough of the header to recognize it.

3) on the your_choice file, at offsets starting on block boundaries (0, 4096, 8192, etc) check if the first 16 bytes match the 16 bytes of your sample.

{You might get lucky and just check block 65 and 66 first).

But anywho - that is how to find where on the raw device you should align the start of the uImage file that you are writing.

If that isn't "hospitable and effective help" enough for you, go somewhere else.

[variousvirgil]

@knc1: Well, I was just not sure whether the format is not changing from to version to version so that I can use the data gathered from 5.6.1 to judge the layout, and I'm now free from all inhibitions. Thank you for the important information!
It's really hospitable and effective help!

I'm not a native speaker, and I have to use dictionaries often, so I cannot know whether my wording is making sense...

[knc1]

Originally Posted by variousvirgil

@knc1: Well, I was just not sure whether the format is not changing from to version to version so that I can use the data gathered from 5.6.1 to judge the layout, and I'm now free from all inhibitions. Thank you for the important information!
It's really hospitable and effective help!

I'm not a native speaker, and I have to use dictionaries often, so I cannot know whether my wording is making sense...

It might be changing from firmware version to firmware version since the start of Amazon shipping complete images.
(About the time those directions where written.)

I don't think anyone ever checked if or when they change the storage layout.

Geekmaster wrote a tool to locate the start of the kernel and the start of the partitioned area.
I think since then, people just leave it up to his tool to find it.

- - - - -

Of course, u-boot "knows" where to start reading the raw device from.
That information is contained in its environment settings (as a byte offset, not a block offset).

You can display that information while in u-boot with the "printenv" command.

[Ruskie_it]

Originally Posted by variousvirgil

the updater of 5.6.1 is really evil.

Hi virgil, what do you exactly mean by that?

[knc1]

Originally Posted by Ruskie_it

Hi virgil, what do you exactly mean by that?

It tries its best to **not** install our non-Amazon packages.

Which just means that we will have to transition away from using the Amazon provided package installer during the coming year.

[NiLuJe]

To be precise, it chucks the current format we're using. Working around that and still using the OTA Updater can (for now) still be done, but that's mostly irrelevant right now, since we can do it ourselves w/ MRPI. That's an issue best left discussed if/when we get an 'easy' KT2/KV jailbreak, since we possibly can't run KUAL (and thus MRPI) on these.