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

[Sam Protsenko]

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.

[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)
-- 
2.20.1