From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-out.m-online.net (mail-out.m-online.net [212.18.0.10]) by ozlabs.org (Postfix) with ESMTP id 80B83DDE2F for ; Tue, 11 Sep 2007 19:40:41 +1000 (EST) Subject: SYSFS: need a noncaching read From: Heiko Schocher To: linux-kernel@vger.kernel.org Content-Type: text/plain Date: Tue, 11 Sep 2007 11:43:17 +0200 Message-Id: <1189503798.6674.46.camel@Zeus.EmbLux> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, Detlev Zundel Reply-To: hs@denx.de List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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? suggestions are welcome thanks Heiko -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany