Make the length parameter a `size_t` instead of a `intptr_t`.  A signed
value does not make any sense here and just leads to weird behavior if a
negative value is given nonetheless.

See issue card10/firmware#192

Signed-off-by: Rahix <rahix@rahix.de>

In severe error conditions, asynchronous prints will never work.  For
such cases we need a way to make prints happen synchronously again, the
same way it works during early boot.  Add a serial_return_to_synchronous()
function which unconditionally switches the serial driver code to
synchronous mode.

Only use this function in unrecoverable error conditions!

Signed-off-by: Rahix <rahix@rahix.de>

serial_flush() allows flushing the serial buffer from anywhere in
Epicardium.

- When run from thread mode it will flush to UART, CDC-ACM and BLE.
  This is similar to what the serial task would do once it is
  rescheduled.
- When run inside an exception handler, it will only flush to UART
  because CDC-ACM and BLE cannot be flushed from an ISR.  Note that
  characters flushed this way will never appear on the other outputs,
  even if the serial task is scheduled at some point afterwards.

The main use of this function is to ensure output of messages even in
cases of critical failures.

Signed-off-by: Rahix <rahix@rahix.de>

danukeru authored 5 years ago and rahix committed 5 years ago

Previously, race-conditions between multiple serial writes could lead to
memory corruption and weird artifacts like I2C getting stuck.  This
patch introduces a write-streambuffer which queues all messages.

Co-authored-by: Rahix <rahix@rahix.de>
Signed-off-by: danukeru <danukeru@foulab.org>

swym authored 5 years ago and rahix committed 5 years ago

usb/epc_usb
====
Contains device-independent USB implementation, services MAXUSB stack
and is given the actual USB descriptors & callbacks on initialization.
Handles USB events and configures/deconfigures the device accordingly
during the USB setup procedure.

usb/mass_storage & cdcacm
====
Contain device-specific implementations, service MAXUSB's device class
APIs for cdcacm and mass storage.
Here, mass storage is independent of the underlying storage device.

modules/usb
====
Public apic_usb API, configuration and storage device management.
Defines the actual USB device descriptors and services the upc_usb API.

If we want to add SD card functionality, this would be the place to add
it.

Sometimes during initialization, one `log_msg()` intercepts another one,
leading to a whole lot of weird issues in other modules (like I2C).  I
suspect this to be memory corruption of some kind.  The issues can be
fixed by performing serial prints in a critical section, thus ensuring
atomicity of prints.  Note that this does not mean log messages will not
interleave.

The CDC-ACM and BLE-Serial writes cannot be put into a critical section
and are thus a point where this code can still fail.  For now, however,
this fix ensures the race-conditions during startup, where USB and BLE
are not yet running, don't happen anymore.

Signed-off-by: Rahix <rahix@rahix.de>

Closes #67

Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>