Hello,
I am working on porting a Linux VME driver to Xenomai. I am having some
ideas on how to do this, but I would like to have some feedback on this.
There are 2 ways to communicate to devices on the VME bus: memory mapped
and using interrupts. At this moment I setup the memory mapping when the
system starts, and then use these mapped areas to read and write from
the devices. The interrupts are processed using a standard interrupt
handler, and a "Wait for interrupt" IOCTL-call is available to wait for
a specific interrupt. The driver defines several VME devices: some
control devices and some data devices.
My plans for the new driver are to have an RTDM driver next to the
standard Linux driver. I will be using the standard driver for the setup
of the system, like setting up the memory mapping. The RTDM driver will
define a RT-control device to perform the interrupt handling and an RTDM
IOCTL will be used to wait for the interrupts. This way I can have a
RT-thread to process the interrupts.
The reason for this setup are:
* I do not want to rewrite the current driver, as this driver
already has all the functionality needed, except for the
RT-performance.
* The interface to VME devices is done using memory access and no
other SW is needed for this. This means that during operational
use no driver functions will be accessed.
* The memory mapping is not as straight forward in RTDM as it is in
standard Linux: for example there is no mmap function in the
device structure.
* I can still use drivers for VME devices that depend on the current
driver.
Is this the right way to do this, or are there other ways to implement a
driver like this one?
Kind regards,
Johan Borkhuis
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