Both pps_parport and pps_gen_parport are written in a way that they
can't share a port with any other driver. This can result in locking up
the process that loads modules or even the whole kernel if the modules
are compiled in. Use PARPORT_FLAG_EXCL to indicate this.
Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Cc: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add parallel port PPS client. It uses a standard method for capturing
timestamps for assert edge transitions: getting a timestamp soon after an
interrupt has happened.
This is not a very precise source of time information due to interrupt
handling delays. However, timestamps for clear edge transitions are much
more precise because the interrupt handler continuously polls hardware
port until the transition is done.
Hardware port operations require only about 1us so the maximum error
should not exceed this value. This was my primary goal when developing
this client.
Clear edge capture could be disabled using clear_wait parameter.
Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
