Adds support for hardware i2c to the zephyr port. Similar to other ports
such as stm32 and nrf, we only implement the i2c protocol functions
(readfrom and writeto) and defer memory operations (readfrom_mem,
readfrom_mem_into, and writeto_mem) to the software i2c implementation.
This may need to change in the future because zephyr is considering
deprecating its i2c_transfer function in favor of i2c_write_read; in this
case we would probably want to implement the memory operations directly
using i2c_write_read.
Tested with the accelerometer on frdm_k64f and bbc_microbit boards.
CONFIG_NET_NBUF_RX_COUNT no longer exists in Zephyr, for a while. That
means we build with the default RX buf count for a while too, and it works,
so just remove it (instead of switching to what it was renamed to,
CONFIG_NET_PKT_RX_COUNT).
Add CONFIG_NET_DHCPV4, which, after
https://github.com/zephyrproject-rtos/zephyr/pull/5750 works as follows:
static addresses are configured after boot, and DHCP requests are sent
at the same time. If valid DHCP reply is received, it overrides static
addresses.
This setup works out of the box for both direct connection to a
workstation (DHCP server usually is not available) and for connection
to a router (DHCP is available and required).
While this console API improves handling on real hardware boards
(e.g. clipboard paste is much more reliable, as well as programmatic
communication), it vice-versa poses problems under QEMU, apparently
because it doesn't emulate UART interrupt handling faithfully. That
leads to inability to run the testsuite on QEMU at all. To work that
around, we have to suuport both old and new console routines, and use
the old ones under QEMU.
Ideally, these should be configurable from Python (using network module),
but as that doesn't exist, we better off using Zephyr's native bootstrap
configuration facility.
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.