USB stopped working

[roger64]

Hi

I did experiment a freeze once the PW3 was on sleep (without any shock). I finally managed to wake it up by chance (long press, hope, long press...).

It works now nicely without any artefact after waking up. But the USB does not work anymore on v2015.11-1732-g4c8ef61_2018-05-30 and the OTA version right before this one. It's the first time this happens.

USB works like usual on the Kindle so this is not a major problem for me.

[Ken Maltby]

I don't think any USB functions have been added to KOReader, as of now, it has been discussed. The KOReader software should not effect your USB.

Luck;
Ken

[NiLuJe]

@roger64: Yep, it's by design, we cannot support USBMS on the Kindle, because we live there. So instead of crashing in fun and interesting ways or wreaking havoc on the filesystem, USBMS is now completely inhibited. (And, yes, it's new, nothing untoward happened to your device ).

If you plug your device, the device will still charge, KOReader will still be usable, there just won't be any switch to USBMS, it'll be as if you were plugged to a (slow) charger. The only side-effect right now is that the frontlight will be turned off (you might be able to manually turn in back on, though).

A device running in USBNet mode suffers no such drawbacks.

[roger64]

Maybe some file is corrupt somewhere, there must be a reason if it does not work anymore. I'll keep it this way some days and if it persists, I shall reinstall.

[NiLuJe]

@roger64: Err, what? Did my previous answer fall into a black hole? Or do we have a very different definition/understanding of what you mean by "USB doesn't work"?

[roger64]

Originally Posted by NiLuJe

@roger64: Err, what? Did my previous answer fall into a black hole? Or do we have a very different definition/understanding of what you mean by "USB doesn't work"?

Sorry for the "black hole", it was certainly unintended. When I write "usb is not working with koreader", I mean that when I connect my PW3 to my computer with an USB cable, koreader being open, no file appear on the computer. If I swich to Kindle, the files appear as usual.

So I reread your note. I realize now to my surprise that this shutting off of koreader has been done on purpose... so I shall not reinstall koreader (though I wish I could downgrade it).

[cramoisi]

@roger64 : I'm really sure you shouldn't do it but you can revert the thing easily as it's in a sh file : https://github.com/koreader/koreader/pull/3957/files

you just need to reverse platform/kindle/koreader.sh (don't do it)

[NiLuJe]

... which will do horrible things to your device, because it's essentially asking to remove the wheels off of a running car without the car and/or driver being aware of it, and as such having time to park and ask its passengers to step out. (Hey, my crappy analogy for impromptu USBMS almost makes sense ).

That said, I'm genuinely curious as to what was your experience before this fix, because what happened up until now perfectly falls into the mysterious realm of "undefined behavior".

(And most likely veering into the "oh shit" side of "undefined behavior").

At the very least, KOReader crashed. At worst, the kernel hung. In between there, you could experience a volumd and/or awesome induced softlock. Any of these could potentially be cause for data loss and/or filesystem curruption.
So, yeah, genuinely curious as to how your device behaved .

Because, agreed, it's a pretty harsh way of avoiding the problem, but I'm not seeing any better ways to avoid the worst on unsuspecting users, unfortunately ;/.

[cramoisi]

for science !

[roger64]

Well my reaction has been knee-jerk. Oh shit, still another unwanted unguaranteed change... Sorry for that.

I will not dare to discuss the technical reasons behind such a change which are very probably rock-solid. As I never before experimented USB problems with koreader on my PW3 (I had been told once by a developer whose name I forgot, that the integration of koreader with Kindle was "native", contrary to what happens with Kobo for example), I instinctively felt it was more of a regression than a progress.

This said, I do notice some display improvements. I get less artefacts whan koreader is going out of sleep, if only. On a broader view, it probably concurs to the stability of the software.

I remember using some years ago a small program which could display files seamlessly between kindle and koreader. After some tries, I discarded it because of its instability. Curiously this same instability had never been openly discussed...

[NiLuJe]

@roger64: No worries .

Yeah, we don't support USBMS either on the Kobo (because unlike on Kindle, the stock system is pretty monolithic, and since we kill it, we "lose" any low-level stuff it might have done for us).

While it's true that, on Kindle, since the stock is system is *extremely* modular, we try to take advantage of that. It's not always as easy as we'd like, but it allows us to leverage a few of its low-level capabilities (of particular interest, this ensures a rock-solid suspend support, since it's the system's ).

I'm still quite interested in how your device behaved and what your interpretation of what was happening was, because it's always interesting to put oneself in a user's shoes. I've been messing/fighting with this particular bit of the system for so long that I have a very specific PoV on it .

And as to why it's never come up until now: err, beats me, we've known that USBMS was a terrible idea for quite a while, I vaguely remember discussions about how we could go about handling it as far back as during the kpdfviewer days. Since KOReader, I can only blame myself for completely forgetting about this, since I'm the main maintainer of the Kindle startup script, and my devices spend roughly 99.99% of their time in USBNet mode -_-".

[roger64]

About USB

I've never had to fight with my USB, either with Kindle or Koreader. Display of the files had been working quite reliably on PW3.

These last few months, I noticed some artefacts when going out of sleep or leaving USB (screen divided in two or three parts, some coming from Kindle), but just touching it put things back in order. So for me at least, I had no complaints against the USB with koreader. I was thinking that my machine was beginning to feel its age (2 1/2 years).

[NiLuJe]

@roger64: Let's go through it slowly and in order:

* KOReader is running.
* You plug your device to a computer
* The Kindle's default "I'm talking to a PC over USB" screen shows up.
* Kindle content shows up on the PC
(so far, so good).

Now, things potentially start to get interesting:
* Eject & unplug the device from the PC
* Kindle's "I'm talking to a PC over USB" screen goes away.

And then what happens?

* You're thrown back to the Kindle's Homescreen, KOReader isn't running anymore.
OR
* KOReader resumes without any apparent issues.

[roger64]

Indeed.

On second thought, to be better understood, replace the word "artefact" (too generic and unclear) by "mangled screen" which describes better what the user can see.

[NiLuJe]

@roger64: If you mean "holes" in the UI, where you basically see bits of the vanilla UI underneath KOReader, then, yeah, that can happen (on recent-ish FWs especially, >= 5.6.x, IIRC).

I tried taking care of the most glaring ones where possible, but most of it depends on timing and on the screen's reactivity at that specific moment in time (which, itself, depends on a looooot of things), and while in some instances we have a bit of leeway in the timings involved, sometimes, we don't .