On Tuesday, August 24, 2010 16:57:10 Frans Meulenbroeks wrote: > 2010/8/24 Mike Frysinger: > > On Tuesday, August 24, 2010 07:28:00 Frans Meulenbroeks wrote: > >> commit c00e9e68d7f77cc3cf3475203860a66cafeba449: > >> Use already cached fp rather than constantly re-opening things on the > >> fly. breaks gpio operation. > >> It is possible to reuse the cached fp, but then we need to seek to the > >> beginning each time. > >> /sys/class/gpio/gpio*/value contains only one byte so without seek > >> we will get only one byte. > > > > ive changed it to rewind(). however, this sounds like useless overhead > > at the kernel level. i'll start a thread on lkml complaining about > > being forced to make two system calls when one should be sufficient. > > i'd point out that my simple gpio driver design didnt have this > > limitation :P. > > It would be nice to work without the seek. In that case maybe the > clock toggle can be done by writing "010" in one write operation (if > the pulse does not become too small, ofc 011110 could also be used > then. > rewind or fseek does not seem too much of a difference.
last i checked, there are two clocking functions ... one allows buffering and requires higher layers to flush the result, while the other is basically "toggle the line now". so someone might want to look into that if/when the kernel gets support. also, i noticed the gpio cable driver doesnt respect the active frequency. so at the moment, its frequency is basically "go as fast as possible" which could be too fast for some parts. we might have to revisit this at some point when someone complains, but in the mean time, i'll make a note in the source code about it. -mike
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