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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 987F6C433B4 for ; Thu, 29 Apr 2021 11:40:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D2B86143D for ; Thu, 29 Apr 2021 11:40:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233337AbhD2LlT (ORCPT ); Thu, 29 Apr 2021 07:41:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59426 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233011AbhD2LlS (ORCPT ); Thu, 29 Apr 2021 07:41:18 -0400 Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E12FC06138C for ; Thu, 29 Apr 2021 04:40:32 -0700 (PDT) Received: by mail-wm1-x329.google.com with SMTP id s82so595386wmf.3 for ; Thu, 29 Apr 2021 04:40:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=9eUkxQOkVtQDsF9AwW1ogEMCTUXqtTF+d+YnllLLjEg=; b=YAoccdsFiPYqGJfIn/ZoRDYWHv/Q3ZF9Y7n7AwQ+X+Q/4CVynOl4O3Wh6JMNCT5IzY uqXjovTfjYnCWXAwNTd60dzQl0DSuFTl8otxbfI1/O9wbJajUpUrTGI+LMX82EYFW7dH NSheFuQjSO6DgbF9h+juTkX/elPK08f0uKcS0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=9eUkxQOkVtQDsF9AwW1ogEMCTUXqtTF+d+YnllLLjEg=; b=oiqEikSI8647MalTqF8PJ7pVW4fej8G6tkEruP8w75vVpq+TmMeK+NiJp2a26is6uh 9vCGo5EjZQlH2sc8RyoLvoRWcZ641pRKG8Qdw1wOgT4xzn7vpSSs7zlXBnEspYmtsfVs 1W0cj1uGTSmMPvJR7kiLgPNuUNruw2yB+UgvzL0i7UwiT5GSA23HaYG6E6x73BkTNykG 1yCpCtmyMMMOATt3fqmTPBpyB9u8oCQY8piIL+Uvk3L94qCwAu0ECsc/aJD9qL8hMJ8A WbitldhT7vXU0Fm+pVQTOhKCJefeQ35Kr+vzVdLicQdvCaTmttCN2MMsvGX/M2ghRZLd dIEg== X-Gm-Message-State: AOAM532ziNuMBoLieOxDuQiXDbhWRlV7Jmmz2f4PQKmVVKJ/dKYpYOwe 6/HosNgtJZPNtUDM0tTRNsQbdg== X-Google-Smtp-Source: ABdhPJy6P94bq1TrQU8Q0uKhEm5PJtAjsM/T+lraIRT6DDfyHLGiD3njKgkzDmrd0SOO3lsGi098Fg== X-Received: by 2002:a1c:f618:: with SMTP id w24mr36312197wmc.93.1619696430950; Thu, 29 Apr 2021 04:40:30 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id q12sm1942738wrx.17.2021.04.29.04.40.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Apr 2021 04:40:30 -0700 (PDT) Date: Thu, 29 Apr 2021 13:40:28 +0200 From: Daniel Vetter To: Hans de Goede Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Daniel Vetter , David Airlie , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Greg Kroah-Hartman , Guenter Roeck , Heikki Krogerus , intel-gfx , dri-devel@lists.freedesktop.org, platform-driver-x86@vger.kernel.org, linux-usb@vger.kernel.org Subject: Re: [PATCH 1/9] drm/connector: Make the drm_sysfs connector->kdev device hold a reference to the connector Message-ID: References: <20210428215257.500088-1-hdegoede@redhat.com> <20210428215257.500088-2-hdegoede@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210428215257.500088-2-hdegoede@redhat.com> X-Operating-System: Linux phenom 5.10.32scarlett+ Precedence: bulk List-ID: X-Mailing-List: platform-driver-x86@vger.kernel.org On Wed, Apr 28, 2021 at 11:52:49PM +0200, Hans de Goede wrote: > Userspace could hold open a reference to the connector->kdev device, > through e.g. holding a sysfs-atrtribute open after > drm_sysfs_connector_remove() has been called. In this case the connector > could be free-ed while the connector->kdev device's drvdata is still > pointing to it. > > Give drm_connector devices there own device type, which allows > us to specify our own release function and make drm_sysfs_connector_add() > take a reference on the connector object, and have the new release > function put the reference when the device is released. > > Giving drm_connector devices there own device type, will also allow > checking if a device is a drm_connector device with a > "if (device->type == &drm_sysfs_device_connector)" check. > > Note that the setting of the name member of the device_type struct will > cause udev events for drm_connector-s to now contain DEVTYPE=drm_connector > as extra info. So this extends the uevent part of the userspace API. > > Signed-off-by: Hans de Goede Are you sure? I thought sysfs is supposed to flush out any pending operations (they complete fast) and handle open fd internally? Also I'd assume this creates a loop since the connector holds a reference on the kdev? -Daniel > --- > drivers/gpu/drm/drm_sysfs.c | 54 +++++++++++++++++++++++++++++++------ > 1 file changed, 46 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c > index f0336c804639..c344c6d5e738 100644 > --- a/drivers/gpu/drm/drm_sysfs.c > +++ b/drivers/gpu/drm/drm_sysfs.c > @@ -50,6 +50,10 @@ static struct device_type drm_sysfs_device_minor = { > .name = "drm_minor" > }; > > +static struct device_type drm_sysfs_device_connector = { > + .name = "drm_connector", > +}; > + > struct class *drm_class; > > static char *drm_devnode(struct device *dev, umode_t *mode) > @@ -271,30 +275,64 @@ static const struct attribute_group *connector_dev_groups[] = { > NULL > }; > > +static void drm_sysfs_connector_release(struct device *dev) > +{ > + struct drm_connector *connector = to_drm_connector(dev); > + > + drm_connector_put(connector); > + kfree(dev); > +} > + > int drm_sysfs_connector_add(struct drm_connector *connector) > { > struct drm_device *dev = connector->dev; > + struct device *kdev; > + int r; > > if (connector->kdev) > return 0; > > - connector->kdev = > - device_create_with_groups(drm_class, dev->primary->kdev, 0, > - connector, connector_dev_groups, > - "card%d-%s", dev->primary->index, > - connector->name); > + kdev = kzalloc(sizeof(*kdev), GFP_KERNEL); > + if (!kdev) > + return -ENOMEM; > + > + device_initialize(kdev); > + kdev->class = drm_class; > + kdev->type = &drm_sysfs_device_connector; > + kdev->parent = dev->primary->kdev; > + kdev->groups = connector_dev_groups; > + kdev->release = drm_sysfs_connector_release; > + dev_set_drvdata(kdev, connector); > + > + r = dev_set_name(kdev, "card%d-%s", dev->primary->index, connector->name); > + if (r) > + goto err_free; > + > DRM_DEBUG("adding \"%s\" to sysfs\n", > connector->name); > > - if (IS_ERR(connector->kdev)) { > - DRM_ERROR("failed to register connector device: %ld\n", PTR_ERR(connector->kdev)); > - return PTR_ERR(connector->kdev); > + r = device_add(kdev); > + if (r) { > + DRM_ERROR("failed to register connector device: %d\n", r); > + goto err_free; > } > > + /* > + * Ensure the connector object does not get free-ed if userspace still has > + * references open to the device through e.g. the connector sysfs-attributes. > + */ > + drm_connector_get(connector); > + > + connector->kdev = kdev; > + > if (connector->ddc) > return sysfs_create_link(&connector->kdev->kobj, > &connector->ddc->dev.kobj, "ddc"); > return 0; > + > +err_free: > + put_device(kdev); > + return r; > } > > void drm_sysfs_connector_remove(struct drm_connector *connector) > -- > 2.31.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch