Stuart,
i think i get it now, sorry i basically asked the same question twice.
the idea of data transfer was stuck in my head. shocking.
well i think i'll go read Rubini's now.
regards, emeel.
Emeel wrote:
>
> 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 clear picture of kernel drivers (although a bit out of date wrt current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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