Driver with hard RT requiremnets

[Ran Shalit]

On Mon, Dec 5, 2016 at 4:35 PM, Greg KH <greg at kroah.com> wrote:

> On Mon, Dec 05, 2016 at 04:24:05PM +0200, Ran Shalit wrote:
> > Hello,
> >
> > We need to support serial driver with real time requirements (towards
> specific
> > device with RT demands):
> > Every 5.3msec receive 100 bytes and 1.3msec afterwards send 100 bytes.
> >
> > 1. Does kernel support real-time of such hard requirements ?
>
> It depends on the hardware you are using, does your hardware provide
> enough processing power and lack of harware interruptions (i.e. SMI) to
> allow this to work properly?
>
> > 2. Is it matter if we do the exact bytes send/receive from kernel or
> userspace,
> > i.e. is kernel more real-time than userspace ?
>
> It depends on your userspace code, people write real-time Java code in
> userspace just fine.
>
> > 3. Is mainline kernel unable to support such requirements and we better
> use RT
> > patch such as xemonai ?
>
> Why not try it out yourself and see?  You have the code and the hardware
> to test, you don't need us to tell you if this works or not :)
>

Hi,

I mean that the requirements doesn't allow missing of these time intervals
for send/receive.
Say If I'll test and it shall work OK, does it mean that in a more loaded
usage (more threads in a future application), it shall still function
correctly with the same kernel (from mainline) ?

I also wanted to ask if it is doing real-time in kernel is better than
doing it in userspace ?

Since we have some doubts if kernel can support such hard requirements, I
raised this question. I know that Xenomai was created to make kernel hard
real-time.


Thank you for any feedback.
Ran


>
> good luck!
>
> greg k-h
>
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