Create a shared memory pool, between driver and app, and only write the
pointers into the FIFO.
Thank You.
Eric O. Heinicke [EMAIL PROTECTED]
BAE SYSTEMS Voice:631.262.8644
Fax: 631.262.8657
One Hazeltine Way, MS 1-78
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> -----Original Message-----
> From: Calin A. Culianu [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, September 25, 2001 13:27
> To: [EMAIL PROTECTED]
> Subject: [rtl] RTF
>
>
>
> Let's say the RT Kernel thread is writing into an rtf as fast
> or slightly
> faster than the user process can consume the data. There are no
> guarantees that the user process won't hiccup on the data, are there?
>
> Let's say the rt kernel task keeps writing the string:
>
> "realtime" into a fifo of precisely 8 bytes, every, oh i dunno, 100ms.
>
> Now let's say my user process tries to read those 8 bytes.
> But after the
> 4th byte was interrupted. He just gets the word 'time', and 'real'
> is left in the fifo. Now, the rt-task runs before the user task and
> pushes in the word 'realtime' again, clobbering the word 'real' that
> was left. The user process tries to read in what he thinks are the
> remaining 4 bytes from the fifo, but he gets the word 'time' again.
>
> (Ok, so in reality the word would be written into the fifo
> backwards as:
> 'emitlaer' and read in forwards as 'realtime' but you get my point,
> right?).
>
> My question is this: What steps should a programmer take to
> at least be
> able to discard erroneous or hiccupped data coming from the rt-thread?
> More specifically, I plan on writing structs into the fifo and reading
> them in userland. I was thinking of delimiting these structs
> with a few
> bytes that would never appear in the structs themselves, that
> way the user
> process can synchronize its reads somewhat to those
> delimiters, as well as
> use magic numbers in the structs to identify the need to synchronize.
>
> Is this overkill? Is there a simpler approach to this
> dilemma? Should I
> not be worrying about this as the rtf driver is smarter than I give it
> credit for?
>
> Please help me overcome my fears,
>
> -Calin
>
> PS: I feel kind of uncomfortable writing structs in the fifo
> in the first
> place, but am too lazy to textualize the data and then
> re-parse it later.
> :/
>
>
>
>
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