hi all,
thanks Stuart,
may i add a few more bits to the original question please?
i'd like to know at what point in the frank_module.c code does the
transfer between the /dev/rtfx and RT_FIFO created by rtf_ceate(1,xxx)
take place? i mean which line of code would initiate this transfer of
data? i need to modify this example to do some random data acquisition
in real time so i need to know the process to move the acquired data
from the RT domain to the user space.
also is there a upper size restriction on the real time buffers?
regards, emeel.
Stuart Hughes wrote:
>
> Emeel wrote:
>
> > i have not yet worked out how the data is transfered from the fifos that
> > were written to in the thread code to the files /dev/rtfx... that were
> > printed out in the end.
> > can anyone please let me know?
> >
> > thanks in advance.
> >
>
> Hi Emeel,
>
> There is not real file involved, just the special
> device inode. Roughly, when the user code calls read, a trap to kernel
> space is made, and the driver associated with rtfx is called, at this
> point the data stored in the per-fifo buffer is copied to the user space
> programs buffer referenced by the read call, on return from the kernel
> the user buffer will have the fifo data available for printing.
>
> Take a look at Linux device drivers by Alessandro Rubini, this gives a
> clear picture of kernel drivers (although a bit out of date wrt current
> kernel versions, I think a second edition should be out 'real soon')
>
> Regards, Stuart
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