[U-Boot] [PATCH v2 2/2] fastboot: Fix slot names reported by getvar

Tue Jun 18 21:10:04 UTC 2019

On Tue, 18 Jun 2019 17:34:54 +0300
Sam Protsenko <semen.protsenko at linaro.org> wrote:

> Hi Lukasz,
> 
> Seems like the versioning is basically useless in fastboot USB
> protocol. It exists, but only host requests the version from device
> (bootloader), like "fastboot getvar version". It always returns "0.4"
> [1], and it was unchanged for 5 years or so. I didn't find any
> handshake with protocol version exchange. Alas, as I mentioned before,
> we probably can't keep the backward compatibility in universal way.
> The only way I see to make U-Boot work with both "a" and "_a"
> prefixes, is to introduce some new config option or dedicated
> environment variable, so that user can specify which format should be
> used.
> 
> I suggest merging this as is, as we don't have any users for slotted
> partitions in upstream U-Boot anyway, at this moment. If need arises,
> we can add option or variable later. Of course, I don't suggest to
> merge this right now, as codebase is frozen, and this is not an ideal
> bugfix and can even break backward compatibility. Let's take it when
> merge window opens.
> 
> Please tell me what is the preferred course of actions on this one,
> from your point of view.

As you stated in the other mail - you shall prepare some fix for
current code base (without the _a suffix) for this release. Please
proceed.

Regarding the supported features - maybe we shall introduce new env
variable - like fastboot_version = "0.5" (then - 0.6, 0.7).

And in U-Boot just decide which set of features would be 0.5 or 0.6.

Then, we can also use Kconfig option to enable needed features.

Otherwise, we will have regressions all the time as the "fastboot"
protocol changes without any notice in the versioning (inside the
protocol).

> 
> Thanks!
> 
> [1]
> http://git.denx.de/?p=u-boot.git;a=blob;f=drivers/fastboot/fb_getvar.c;h=4268628f5ef0210507c5d23f2e4209b2afc07029;hb=refs/heads/master#l84
> [2]
> https://android.googlesource.com/platform/system/core/+/9bfecb0e3444306ec57d7fafe4a99a47d3848c17%5E%21/#F0
> 
> On Sat, Jun 15, 2019 at 6:29 PM Lukasz Majewski <lukma at denx.de> wrote:
> >
> > Hi Sam,
> >  
> > > Fastboot tool recently underwent changes w.r.t. A/B slot format:
> > >   1. In commit [1] the new slot format was introduced, according
> > > to new A/B specification [2]. New slot format is "a", and old
> > > format "_a" is now considered legacy.
> > >   2. In commit [3] the legacy format "_a" was fixed and fastboot
> > > tool should support both "a" and "_a" slot formats now.
> > >   3. Finally, commit [4] drops the legacy slot format ("_a")
> > > completely. That makes the latest fastboot tool incompatible with
> > > "_a" format.
> > >
> > > Last change leads to next error, when running "fastboot flash"
> > > with current U-Boot:
> > >
> > >     $ fastboot flash boot boot.img
> > >     Sending 'boot__a' (11301 KB)    OKAY [  0.451s]
> > >     Writing 'boot__a'               FAILED (remote: 'cannot find
> > > partition') fastboot: error: Command failed
> > >
> > > To overcome this issue we should report slot names in "a" format
> > > instead of "_a". Of course, this change breaks U-Boot
> > > compatibility with older fastboot tools, but that shouldn't be a
> > > problem as A/B is not implemented in U-Boot yet, and there are
> > > not users for slotted partitions out there anyway. This fact can
> > > be checked like this:
> > >
> > >     $ grep -Ir \b'boot_a\b' *
> > >
> > > Let's use new slot format in order to fix "fastboot flash" with
> > > slotted partitions and to be in sync with AOSP master.
> > >
> > > With this patch, U-Boot depends on most recent fastboot tool
> > > (patch [1] or later), for working with slotted partitions.  
> >
> > Is there any "version" number scheme for the fastboot protocol
> > specification?
> >
> > I do remember that in the past there were some mismatches for some
> > "fastboot" specification depending on vendor. Now it turns out that
> > there is a problem between AOSP versions ...
> >
> > (My point is that for example even lthor had version number for
> > specification update. Is something similar for fastboot?).
> >  
> > >
> > > [1]
> > > https://android.googlesource.com/platform/system/core/+/8091947847d5e5130b09d2ac0a4bdc900f3b77c5
> > > [2]
> > > https://source.android.com/devices/tech/ota/ab/ab_implement#partitions
> > > [3]
> > > https://android.googlesource.com/platform/system/core/+/04396f62da6150b94e02d50e5302fd980048833d
> > > [4]
> > > https://android.googlesource.com/platform/system/core/+/42b18a518bac85c3eea14206f6cbafbd1e98a31f
> > >
> > > Signed-off-by: Sam Protsenko <semen.protsenko at linaro.org>
> > > ---
> > > Changes in v2:
> > >   - don't change slot format in "slot-suffixes" variable (it's now
> > >     dropped in [PATCH 1/2])
> > >   - improve commit message
> > >
> > >  drivers/fastboot/fb_getvar.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/fastboot/fb_getvar.c
> > > b/drivers/fastboot/fb_getvar.c index f89c7f62e6..9ee5054485 100644
> > > --- a/drivers/fastboot/fb_getvar.c
> > > +++ b/drivers/fastboot/fb_getvar.c
> > > @@ -174,8 +174,8 @@ static void getvar_platform(char
> > > *var_parameter, char *response)
> > >  static void getvar_current_slot(char *var_parameter, char
> > > *response) {
> > > -     /* A/B not implemented, for now always return _a */
> > > -     fastboot_okay("_a", response);
> > > +     /* A/B not implemented, for now always return "a" */
> > > +     fastboot_okay("a", response);
> > >  }
> > >
> > >  #if CONFIG_IS_ENABLED(FASTBOOT_FLASH)  
> >
> >
> >
> >
> > Best regards,
> >
> > Lukasz Majewski
> >
> > --
> >
> > DENX Software Engineering GmbH,      Managing Director: Wolfgang
> > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > lukma at denx.de  

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma at denx.de
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