On Wed, 2007-09-12 at 12:05 +1000, David Gibson wrote: > On Tue, Sep 11, 2007 at 11:43:17AM +0200, Heiko Schocher wrote: > > Hello, > > > > I have developed a device driver and use the sysFS to export some > > registers to 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 ... :-( > > > > Is there a way to retrigger the reads (in that way, that the sysFS > > rereads the values from the driver), without closing and opening the > > sysFS Files? Or must I better use the ioctl () Driver-interface for > > exporting these registers? > > > > I am asking this, because I must read every 10 ms 2 registers, so > > doing a open/read/close for reading one registers is a little bit too > > much overhead. > > > > I made a sysFS seek function, which retriggers the read, and that works > > fine, but I have again 2 syscalls, whats also is not optimal. > > > > Or can we make a open () with a (new?)Flag, that informs the sysFS to > > always reread the values from the underlying driver? > > > > Or a new flag in the "struct attribute_group" in include/linux/sysfs.h, > > which let the sysfs rereading the values? > > This sounds more like sysfs is really not the right interface for > polling your registers. You would probably be better off having your > driver export a character device from which the register values could > be read. I thought relay(fs) was the trendy way to do this these days? Documentation/filesystems/relay.txt cheers -- Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person
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