Darmok is a device subsystem which provides interfaces for communication with the HIPOS board controller via the serial line.
The HIPOS board controller is a microcontroller
that is serially attached to the main ARM processor. You will need the patched
kernel of the HIPOS project to execute the
darmok code. In order to use its functionality you have to enable DARMOK_CORE
in the kernel config file. All of the high level darmok kernel drivers depend
on drbcc-core.
The kernel module and compiled-in code provide an optional legacy tty interface named 'drbcc-raw' which can be used with the userspace drbcc commandline tool of the HIPOS project. If activated in the kernel config it also provides an interface to the rtc device (if applicable) and the hardware watchdog. The darmok core component is implemented using a tty line discipline.
+-------------+-----------------+----------------+
| hwclock, .. | commandline- | watchdog,.. | user space
| | drbcc-tool | |
+-------------+-----------------+----------------+
+-------------+-----------------+----------------+
| drbcc-rtc | drbcc-raw | drbcc-watchdog | kernel space
+-------------+-----------------+----------------+
| drbcc-core |
+------------------------------------------------+
| serial driver (8250.c) |
+------------------------------------------------+
+------------------------------------------------+
| board controller | hardware
+------------------------------------------------+
The module drbcc-core provides an interface to the board controller
functionality. To exchange messages with the board controller the appropriate
values in struct bcc_packet need to be set.
Required entries:
- cmd: see drbcc_ll.h for command options
- data: depending on command (see drbcc_ll.h)
- payloadlen: number of data bytes passed with the command
The other fields must not be filled since they are only used internally in drbcc-core.
The module code should then call the darmok-core function transmit_packet() which will block until the transaction has been completed. The board controller response is filled into struct bcc_packet which is passed to transmit_packet() as a function argument.
The darmok driver subsystem provides several device drivers.
The legacy interface /dev/drbcc-raw allows the use of the command-line drbcc-tool which supports the usage of all commands the board controller supports. It resembles the communication of the command line tool over the serial interface which was used before work on darmok began. It only works with the HIPOS drbcc command line tool.
The watchdog driver is represented by the device file /dev/watchdog. It
supports the system calls WDIOC_SETOPTIONS (supported flags:
WDIOS_DISABLECARD, WDIOS_ENABLECARD), WDIOC_KEEPALIVE,
WDIOC_SETTIMEOUT, and WDIOC_GETTIMEOUT. If the user space watchdog calls
WDIOS_DISABLECARD the kernel watchdog is in charge of kicking the watchdog.
The RTC device driver is represented by /dev/rtcX, where X is a number depending on the kernel configuration. If, for example, there is another RTC device configured to be compiled into the kernel, this device might be registered first with the RTC device subsystem and named /dev/rtc0. Darmok's RTC device would then be represented by /dev/rtc1.
Further device drivers (e.g. gpio) will eventually be implemented using drbcc-core as an interface.