On Wed, Sep 12, 2007 at 01:13:32PM +0200, Heiko Schocher wrote: > Hello Greg > > Am Mittwoch, den 12.09.2007, 03:01 -0700 schrieb Greg KH: > > On Wed, Sep 12, 2007 at 07:32:07AM +0200, Robert Schwebel wrote: > > > On Tue, Sep 11, 2007 at 11:43:17AM +0200, Heiko Schocher wrote: > > > > I have developed a device driver and use the sysFS to export some > > > > registers to userspace. > > > > > > Uuuh, uggly. Don't do that. Device drivers are there to abstract things, > > > not to play around with registers from userspace. > > > > > > > I opened the sysFS File for one register and did some reads from this > > > > File, but I alwas becoming the same value from the register, whats not > > > > OK, because they are changing. So I found out that the sysFS caches > > > > the reads ... :-( > > > > > > Yes, it does. What you can do is close()ing the file handle between > > > accesses, which makes it work but is slow. > > > > Do an lseek back to 0 and then re-read, you will get called in your > > driver again. > > No thats not true. I thought this too, but if I make a: > > seek (fd, 0L, SEEK_SET); > > in Userspace, there is no retrigger in the sysFS, my driver is *not* > called again. So I made a own sysfs_seek function, which does retrigger > the driver ...
Hm, are you sure? Otherwise the poll() stuff would not work at all. > Is this really wanted in the sysFS, that there is no way to retrigger a > read? Yes, use the sysfs poll/select stuff to do that. And "sysfs" has no upper-case letters :) thanks, greg k-h _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev