Merge tag 'v1.9.1'2.0.0-alpha.0

Fixes for stmhal USB mass storage, lwIP bindings and VFS regressions

This release provides an important fix for the USB mass storage device in
the stmhal port by implementing the SCSI SYNCHRONIZE_CACHE command, which
is now require by some Operating Systems.  There are also fixes for the
lwIP bindings to improve non-blocking sockets and error codes.  The VFS has
some regressions fixed including the ability to statvfs the root.

All changes are listed below.

py core:
- modbuiltins: add core-provided version of input() function
- objstr: catch case of negative "maxsplit" arg to str.rsplit()
- persistentcode: allow to compile with complex numbers disabled
- objstr: allow to compile with obj-repr D, and unicode disabled
- modsys: allow to compile with obj-repr D and PY_ATTRTUPLE disabled
- provide mp_decode_uint_skip() to help reduce stack usage
- makeqstrdefs.py: make script run correctly with Python 2.6
- objstringio: if created from immutable object, follow copy on write policy

extmod:
- modlwip: connect: for non-blocking mode, return EINPROGRESS
- modlwip: fix error codes for duplicate calls to connect()
- modlwip: accept: fix error code for non-blocking mode
- vfs: allow to statvfs the root directory
- vfs: allow "buffering" and "encoding" args to VFS's open()
- modframebuf: fix signed/unsigned comparison pendantic warning

lib:
- libm: use isfinite instead of finitef, for C99 compatibility
- utils/interrupt_char: remove support for KBD_EXCEPTION disabled

tests:
- basics/string_rsplit: add tests for negative "maxsplit" argument
- float: convert "sys.exit()" to "raise SystemExit"
- float/builtin_float_minmax: PEP8 fixes
- basics: convert "sys.exit()" to "raise SystemExit"
- convert remaining "sys.exit()" to "raise SystemExit"

unix port:
- convert to use core-provided version of built-in import()
- Makefile: replace references to make with $(MAKE)

windows port:
- convert to use core-provided version of built-in import()

qemu-arm port:
- Makefile: adjust object-file lists to get correct dependencies
- enable micropython.mem_*() functions to allow more tests

stmhal port:
- boards: enable DAC for NUCLEO_F767ZI board
- add support for NUCLEO_F446RE board
- pass USB handler as parameter to allow more than one USB handler
- usb: use local USB handler variable in Start-of-Frame handler
- usb: make state for USB device private to top-level USB driver
- usbdev: for MSC implement SCSI SYNCHRONIZE_CACHE command
- convert from using stmhal's input() to core provided version

cc3200 port:
- convert from using stmhal's input() to core provided version

teensy port:
- convert from using stmhal's input() to core provided version

esp8266 port:
- Makefile: replace references to make with $(MAKE)
- Makefile: add clean-modules target
- convert from using stmhal's input() to core provided version

zephyr port:
- modusocket: getaddrinfo: Fix mp_obj_len() usage
- define MICROPY_PY_SYS_PLATFORM (to "zephyr")
- machine_pin: use native Zephyr types for Zephyr API calls

docs:
- machine.Pin: remove out_value() method
- machine.Pin: add on() and off() methods
- esp8266: consistently replace Pin.high/low methods with .on/off
- esp8266/quickref: polish Pin.on()/off() examples
- network: move confusingly-named cc3200 Server class to its reference
- uos: deconditionalize, remove minor port-specific details
- uos: move cc3200 port legacy VFS mounting functions to its ref doc
- machine: sort machine classes in logical order, not alphabetically
- network: first step to describe standard network class interface

examples:
- embedding: use core-provided KeyboardInterrupt object

1 files changed, 65 insertions, 0 deletions

diff --git a/docs/library/uio.rst b/docs/library/uio.rst
index 9b4c87df8..1239c6394 100644
--- a/docs/library/uio.rst
+++ b/docs/library/uio.rst
@@ -7,6 +7,71 @@
 This module contains additional types of stream (file-like) objects
 and helper functions.
 
+Conceptual hierarchy
+--------------------
+
+.. admonition:: Difference to CPython
+   :class: attention
+
+   Conceptual hierarchy of stream base classes is simplified in MicroPython,
+   as described in this section.
+
+(Abstract) base stream classes, which serve as a foundation for behavior
+of all the concrete classes, adhere to few dichotomies (pair-wise
+classifications) in CPython. In MicroPython, they are somewhat simplified
+and made implicit to achieve higher efficiencies and save resources.
+
+An important dichotomy in CPython is unbuffered vs buffered streams. In
+MicroPython, all streams are currently unbuffered. This is because all
+modern OSes, and even many RTOSes and filesystem drivers already perform
+buffering on their side. Adding another layer of buffering is counter-
+productive (an issue known as "bufferbloat") and takes precious memory.
+Note that there still cases where buffering may be useful, so we may
+introduce optional buffering support at a later time.
+
+But in CPython, another important dichotomy is tied with "bufferedness" -
+it's whether a stream may incur short read/writes or not. A short read
+is when a user asks e.g. 10 bytes from a stream, but gets less, similarly
+for writes. In CPython, unbuffered streams are automatically short
+operation susceptible, while buffered are guarantee against them. The
+no short read/writes is an important trait, as it allows to develop
+more concise and efficient programs - something which is highly desirable
+for MicroPython. So, while MicroPython doesn't support buffered streams,
+it still provides for no-short-operations streams. Whether there will
+be short operations or not depends on each particular class' needs, but
+developers are strongly advised to favor no-short-operations behavior
+for the reasons stated above. For example, MicroPython sockets are
+guaranteed to avoid short read/writes. Actually, at this time, there is
+no example of a short-operations stream class in the core, and one would
+be a port-specific class, where such a need is governed by hardware
+peculiarities.
+
+The no-short-operations behavior gets tricky in case of non-blocking
+streams, blocking vs non-blocking behavior being another CPython dichotomy,
+fully supported by MicroPython. Non-blocking streams never wait for
+data either to arrive or be written - they read/write whatever possible,
+or signal lack of data (or ability to write data). Clearly, this conflicts
+with "no-short-operations" policy, and indeed, a case of non-blocking
+buffered (and this no-short-ops) streams is convoluted in CPython - in
+some places, such combination is prohibited, in some it's undefined or
+just not documented, in some cases it raises verbose exceptions. The
+matter is much simpler in MicroPython: non-blocking stream are important
+for efficient asynchronous operations, so this property prevails on
+the "no-short-ops" one. So, while blocking streams will avoid short
+reads/writes whenever possible (the only case to get a short read is
+if end of file is reached, or in case of error (but errors don't
+return short data, but raise exceptions)), non-blocking streams may
+produce short data to avoid blocking the operation.
+
+The final dichotomy is binary vs text streams. MicroPython of course
+supports these, but while in CPython text streams are inherently
+buffered, they aren't in MicroPython. (Indeed, that's one of the cases
+for which we may introduce buffering support.)
+
+Note that for efficiency, MicroPython doesn't provide abstract base
+classes corresponding to the hierarchy above, and it's not possible
+to implement, or subclass, a stream class in pure Python.
+
 Functions
 ---------