[U-Boot] [RFC PATCH v1 0/5] Add fastboot UDP support

[Lukasz Majewski]

Hi Alex,

> On Tue, Apr 24, 2018 at 11:24 AM, Alex Deymo <deymo+ at google.com>
> wrote:
> > +Jocelyn.
> >
> > Thanks Alex for taking the time to port this!!  
> 
> It turned out to be a great opportunity to play with coccinelle on
> something trivial, which I'd been meaning to do for ages... the
> refactor to add response into the fastboot_okay/fail call chain was a
> breeze with it.
> 
> > 2018-04-24 11:37 GMT+02:00 Alex Kiernan <alex.kiernan at gmail.com>:  
> >>
> >>
> >> This series merges the fastboot UDP support from AOSP into mainline
> >> U-Boot.
> >>
> >> Open questions:
> >>
> >> - what's the correct way of attributing the original authors? I've
> >> added Co-authored-by, is that right? checkpatch doesn't seem to
> >> know any of the co- tags
> >> - currently there's no NAND support and I've no way of testing
> >> that, so my inclination is towards leaving it like that until
> >> someone with that particular itch to scratch can look at it  
> >
> >
> > Fastboot uses partition names, like "system" and "boot" which have
> > a meaning in the Android partition scheme. For GPT, we just use the
> > partition names as the android names; but if you are booting from
> > some other storage like NAND where you don't have that then you
> > need some mapping glue ("system" --> device and partition number).
> > I've seen U-Boot modifications for several devices where they just
> > stick a table hard-coded in the U-Boot code; which works great for
> > that device but it isn't really a generic approach. Other than
> > handling the names issue, I don't see any problem with supporting
> > NAND here, but a generic way to set global names / alias would be
> > needed for this. 
> 
> With the fastboot NAND support in mainline it looks like we end up in
> mtdparts to deliver that mapping through environment variables. 

When you mentioned about NAND partitions - I also have thought about
mtdparts. They are well supported in mainline.

> No
> actual idea what that looks like when you're driving it.

Many boards use them - so there should not be any issue with finding
examples.

> 
> >>
> >> - you can select both USB and UDP fastboot, but the comments in the
> >>   AOSP code suggest that needs fixing - again, I've no board I can
> >> test USB fastboot on  
> >
> >
> > I thought we checked in the Kconfig that you couldn't enable both.
> > I don't remember the details now but yeah you can't wait for
> > network or USB traffic on the current code.
> >  
> 
> The version I picked from (o-mr1-iot-preview-8) has them as
> independent symbols, but making them a choice would resolve the issue
> for now.
> 
> >> I've not tested all the code paths yet, but the obvious stuff works
> >> (basic interaction, download, boot) - every interaction elicits a
> >> `WARNING: unknown variable: slot-count` on the console; I'm
> >> guessing that my local end is sending a getvar for that, but I've
> >> not investigated.  
> >
> >
> > Yes, there's a bit of different handling of partitions for A/B
> > android devices. Instead of "system" you have two partitions:
> > "system_a" and "system_b" (potentially more although 2 is the most
> > common case) so to know whether you have an old device or a newer
> > device the fastboot client checks the "slot-count" variable.
> > Undefined means of course that you have an old-style device, but if
> > you return something like "2" you would be able to flash "system"
> > on the "slot A" which is translated (again in the fastboot client)
> > to flash "system_a" partition. This is useful when using the higher
> > level operations like flashall/update and you want to specify to
> > flash only "slot A", "slot B" or even both of them. There are other
> > fastboot variables that require some plumbing, such as
> > "has-slot:<partition>" to tell whether "system" is a partition that
> > indeed has the two versions _a and _b. Typically some partitions
> > are twice (like "system" and "boot") and some other are not (like
> > "misc" or "userdata"). Anyway, this as is should work for either
> > old-style partition schemes or by force flashing "system_a" with
> > the system.img. 
> 
> Cool, thanks... that saves me a bunch of investigation!
> 




Best regards,

Lukasz Majewski

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