checking number of parallel ports installed and their port
alexbestms at math.uni-muenster.de
Wed Jul 22 19:31:59 UTC 2009
the ppi manual states that using ioctl with /dev/ppi is extremely slow. i need
the parallel port to be really fast. i need to communicate with a device that
uses asynchronous transfer at a rate of ~ 2 mhz. so i need the full ISA bus
speed to be able to push/pull data to/from the parallel port without any
delays. timing is really critical. if there's a lot of work to do for the
scheduler and the io calls get queued too long the transfer will fail.
plus i want the app to be linux compatible and i don't think ppi exists on
actually i meant: how can i check the available parallel ports from within my
app? is there a syscall i can use or something like that?
Alexey Shuvaev schrieb am 2009-07-22:
> On Wed, Jul 22, 2009 at 12:43:20AM +0200, Alexander Best wrote:
> > hi there,
> > i've written an app in c (and a bit of asm) which needs to do raw
> > parallel
> > port io using the i386 opcodes in/out. to get the number of
> > available parallel
> > ports installed and their addresses i open and mmap /dev/mem and
> > read the
> > address-values from the BIOS area @ 0x408. is there a better way to
> > find out
> > the number of parallel ports installed and their addresses?
> Why not to use /dev/ppi interface?
> man 4 ppi
> It is in GENERIC kernel.
> You don't need assembler then.
> You can look at your dmesg to count all ppc parallel ports:
> ppc0: <Parallel port> port 0x378-0x37f,0x778-0x77f irq 7 drq 3 on
> ppc0: SMC-like chipset (ECP/EPP/PS2/NIBBLE) in COMPATIBLE mode
> ppc0: FIFO with 16/16/9 bytes threshold
> ppc0: [ITHREAD]
> ppbus0: <Parallel port bus> on ppc0
> plip0: <PLIP network interface> on ppbus0
> plip0: [ITHREAD]
> lpt0: <Printer> on ppbus0
> lpt0: [ITHREAD]
> lpt0: Interrupt-driven port
> ppi0: <Parallel I/O> on ppbus0
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