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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 B874AC04EBD for ; Tue, 16 Oct 2018 17:28:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7EF702148D for ; Tue, 16 Oct 2018 17:28:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7EF702148D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728054AbeJQBTg (ORCPT ); Tue, 16 Oct 2018 21:19:36 -0400 Received: from mga05.intel.com ([192.55.52.43]:55348 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727154AbeJQBTf (ORCPT ); Tue, 16 Oct 2018 21:19:35 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Oct 2018 10:28:07 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,389,1534834800"; d="scan'208";a="99721395" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.174]) by fmsmga001.fm.intel.com with SMTP; 16 Oct 2018 10:28:03 -0700 Received: by stinkbox (sSMTP sendmail emulation); Tue, 16 Oct 2018 20:28:03 +0300 Date: Tue, 16 Oct 2018 20:28:03 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Maarten Lankhorst , Rodrigo Siqueira , Gustavo Padovan , Sean Paul , David Airlie , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH v2] drm/drm_vblank: Change EINVAL by the correct errno Message-ID: <20181016172803.GH9144@intel.com> References: <20181015170529.dgzpbm37hbuvqatc@smtp.gmail.com> <57b40f9f-24d2-27de-4895-5a76ff267643@linux.intel.com> <20181016163831.GA31561@phenom.ffwll.local> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20181016163831.GA31561@phenom.ffwll.local> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 16, 2018 at 06:38:31PM +0200, Daniel Vetter wrote: > On Tue, Oct 16, 2018 at 03:36:20PM +0200, Maarten Lankhorst wrote: > > Op 15-10-18 om 19:05 schreef Rodrigo Siqueira: > > > For historical reason, the function drm_wait_vblank_ioctl always return > > > -EINVAL if something gets wrong. This scenario limits the flexibility > > > for the userspace make detailed verification of the problem and take > > > some action. In particular, the validation of “if (!dev->irq_enabled)” > > > in the drm_wait_vblank_ioctl is responsible for checking if the driver > > > support vblank or not. If the driver does not support VBlank, the > > > function drm_wait_vblank_ioctl returns EINVAL which does not represent > > > the real issue; this patch changes this behavior by return EOPNOTSUPP. > > > Additionally, some operations are unsupported by this function, and > > > returns EINVAL; this patch also changes the return value to EOPNOTSUPP > > > in this case. Lastly, the function drm_wait_vblank_ioctl is invoked by > > > libdrm, which is used by many compositors; because of this, it is > > > important to check if this change breaks any compositor. In this sense, > > > the following projects were examined: > > > > > > * Drm-hwcomposer > > > * Kwin > > > * Sway > > > * Wlroots > > > * Wayland-core > > > * Weston > > > * Xorg (67 different drivers) > > > > > > For each repository the verification happened in three steps: > > > > > > * Update the main branch > > > * Look for any occurrence "drmWaitVBlank" with the command: > > > git grep -n "drmWaitVBlank" > > > * Look in the git history of the project with the command: > > > git log -SdrmWaitVBlank > > > > > > Finally, none of the above projects validate the use of EINVAL which > > > make safe, at least for these projects, to change the return values. > > > > > > Change since V1: > > > Daniel Vetter and Chris Wilson > > > - Replace ENOTTY by EOPNOTSUPP > > > - Return EINVAL if the parameters are wrong > > > > > > Signed-off-by: Rodrigo Siqueira > > > --- > > > drivers/gpu/drm/drm_vblank.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c > > > index 98e091175921..80f5a3bb427e 100644 > > > --- a/drivers/gpu/drm/drm_vblank.c > > > +++ b/drivers/gpu/drm/drm_vblank.c > > > @@ -1533,10 +1533,10 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data, > > > unsigned int flags, pipe, high_pipe; > > > > > > if (!dev->irq_enabled) > > > - return -EINVAL; > > > + return -EOPNOTSUPP; > > Change to -EIO? > > > > If userspace would ever print this out, it would print the following > > confusing message to userspace: > > "Operation not supported on transport endpoint" > > You're a bit late, EOPNOTSUPP is not established already in upstream for > this. And -EIO is taken already for "the gpu is dead". > > > > > > > if (vblwait->request.type & _DRM_VBLANK_SIGNAL) > > > - return -EINVAL; > > > + return -EOPNOTSUPP; > > I would keep this -EINVAL, tbh and making it part of the below if statement.. > > We discussed this, it's different: This here is an ioctl flag that's no > longer supported, the below is just an invalid request. Hence different > errno. > > I think you missed a bit with your bikeshed :-) I think I too agree with the -EINVAL here as this flag is never supported, whereas -EOPNOTSUPP seems to mean "this flag is still valid, but not supported by your current hardware/driver configuration". Also drm_invalid_op() uses -EINVAL for deprecated features as well. -- Ville Syrjälä Intel