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authorAlexander Gordeev <lasaine@lvk.cs.msu.su>2011-01-13 04:00:58 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 19:03:21 +0300
commita10203c691eac287664f531b149ddc23056c2f61 (patch)
treec1fc9f1430aeb7d2b73bc0509f85d6477f5c3c26 /Documentation/pps
parent717c033669ed3ceaee8df57d4562fafcc1a6267a (diff)
downloadlinux-a10203c691eac287664f531b149ddc23056c2f61.tar.xz
pps: add parallel port PPS client
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>
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