From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D15EC282DD for ; Wed, 8 Jan 2020 15:08:02 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6B9172087F for ; Wed, 8 Jan 2020 15:08:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6B9172087F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E59636E8A5; Wed, 8 Jan 2020 15:08:01 +0000 (UTC) Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by gabe.freedesktop.org (Postfix) with ESMTPS id 528E16E8A5 for ; Wed, 8 Jan 2020 15:08:01 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 08 Jan 2020 07:08:00 -0800 X-IronPort-AV: E=Sophos;i="5.69,410,1571727600"; d="scan'208";a="215977693" Received: from jnikula-mobl3.fi.intel.com (HELO localhost) ([10.237.66.161]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 08 Jan 2020 07:07:59 -0800 From: Jani Nikula To: Chris Wilson , intel-gfx@lists.freedesktop.org In-Reply-To: <157849474809.2273.10126647469755480457@skylake-alporthouse-com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <600101c8433e7caf9303663fc85a9972fa1f05e7.1575560168.git.jani.nikula@intel.com> <157849474809.2273.10126647469755480457@skylake-alporthouse-com> Date: Wed, 08 Jan 2020 17:07:56 +0200 Message-ID: <87sgkqouk3.fsf@intel.com> MIME-Version: 1.0 Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915/params: add i915 parameters to debugfs X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, 08 Jan 2020, Chris Wilson wrote: > Quoting Jani Nikula (2019-12-05 15:43:40) >> +static int i915_param_int_open(struct inode *inode, struct file *file) >> +{ >> + return single_open(file, i915_param_int_show, inode->i_private); > > What I've always wanted with this style of approach was a means that the > parameter is only set while the debugfs remained open. > > fd = open("/debug/my_parameter", O_WRONLY | O_EXCL); > write(fd, "1", 1); > > ... run test .. > > System reverts to default on process termination, or explicit close(fd). > > I'd make the open implicitly O_EXCL, i.e. return -EBUSY if something > else already holds the parameter set. Or, you can use the O_EXCL to > select between the different modes of operation. > > Moving the parameters to debugfs is more than worth it imo if we can > enable this mode of operation. I understand the use case, and I'd like something like that. But (obviously?) I think the regular use case of 'echo 1 > /debug/my_parameter' needs to work as one would expect. Reading open(2) man page, feels like using O_EXCL for this would be a hack. Granted, it's debugfs to begin with, but still. Makes me a bit hesitant about abusing O_EXCL for this. (Or am I missing something?) BR, Jani. -- Jani Nikula, Intel Open Source Graphics Center _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx