pdx: Rework error reporting when transfering file and channel handles
There is a lot of confusion about reporting errors when passing file
and channel handles over PDX transport between client and service.
Methods like Message::PushFileHandle return an integer which means
both a file handle reference value (if positive) and a possible error
code (if negative). But file handles could contain negative values too
(when they are empty). This is used frequently when passing buffer
fences around (when a fence is not being used, its fd is set to -1).
This results in a special case of when PushFileHandle is called with
a file handle with value of -1, the return value is actually "-errno"
which becomes dependent on a global state (errno is not set by
PushFileHandle itself in case file handle value is negative) and results
in unpredicted behavior (sometimes errno is 0, sometimes its >0).
Cleaned this all up by using Status<T> everywhere we used an int to
pass value payload along with possible error code.
Now the semantics of the calls are more clear.
Bug: 36866492
Test: `m -j32` for sailfish-eng succeeds
Ran unit tests on device (pdx_tests, libpdx_uds_tests, bufferhub_tests,
buffer_hub_queue-test, buffer_hub_queue_producer-test), all pass
Ran CubeSea, NativeTreasureHunt and Ithaca on Sailfish with vrflinger
enabled, was able to use controller and screen rendered correctly.
Change-Id: I0f40c3f356fcba8bc217d5219a0ddf9685e57fd7
47 files changed