- simplify and repair UDS request handling state machine;
- simplify interface used between internal modules;
- implement missing support for nonblocking I/O;
- fix select implementation;
- clean up global variables.
Change-Id: Ia82c5c6f05cc3f0a498efc9a26de14b1cde6eace
Because pipes have no file position. VFS maintained (file) offsets into a
buffer internal to PFS and stored them in vnodes for simplicity, mixing
the responsibilities of filp and vnode objects.
With this patch PFS ignores the position field in REQ_READ and REQ_WRITE
requests making VFS' job a lot simpler.
. all invocations were S or D, so can safely be dropped
to prepare for the segmentless world
. still assign D to the SCP_SEG field in the message
to make previous kernels usable
