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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 C6A67C04EBD for ; Tue, 16 Oct 2018 13:36:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9734E20869 for ; Tue, 16 Oct 2018 13:36:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9734E20869 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 S1727294AbeJPV0z (ORCPT ); Tue, 16 Oct 2018 17:26:55 -0400 Received: from mga01.intel.com ([192.55.52.88]:20967 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727002AbeJPV0y (ORCPT ); Tue, 16 Oct 2018 17:26:54 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Oct 2018 06:36:24 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,388,1534834800"; d="scan'208";a="95675238" Received: from tletko-mobl3.ger.corp.intel.com (HELO [10.252.39.57]) ([10.252.39.57]) by fmsmga002.fm.intel.com with ESMTP; 16 Oct 2018 06:36:21 -0700 Subject: Re: [PATCH v2] drm/drm_vblank: Change EINVAL by the correct errno To: Rodrigo Siqueira , Gustavo Padovan , Sean Paul , David Airlie , Daniel Vetter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org References: <20181015170529.dgzpbm37hbuvqatc@smtp.gmail.com> From: Maarten Lankhorst Message-ID: <57b40f9f-24d2-27de-4895-5a76ff267643@linux.intel.com> Date: Tue, 16 Oct 2018 15:36:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181015170529.dgzpbm37hbuvqatc@smtp.gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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" > > 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.. > if (vblwait->request.type & > ~(_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK | Cheers, Maarten