Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752033Ab2JUHYg (ORCPT ); Sun, 21 Oct 2012 03:24:36 -0400 Received: from mail-da0-f46.google.com ([209.85.210.46]:63694 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751466Ab2JUHYf (ORCPT ); Sun, 21 Oct 2012 03:24:35 -0400 From: Dmitry Torokhov To: Al Viro , Dave Jones Cc: Linus Torvalds , linux-kernel@vger.kernel.org, linux-input@vger.kernel.org Subject: [PATCH 1/2] char_dev: allow setting up and pinning parent devices Date: Sun, 21 Oct 2012 00:24:30 -0700 Message-Id: <1350804271-2449-1-git-send-email-dmitry.torokhov@gmail.com> X-Mailer: git-send-email 1.7.11.7 In-Reply-To: <20121019175046.GP2616@ZenIV.linux.org.uk> References: <20121019175046.GP2616@ZenIV.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2584 Lines: 89 In certain cases (for example when a cdev structure is embedded into another object whose lifetime is controlled by a separate device object) it is beneficial to tie lifetime of another struct device to the lifetime of character device so that related object is not freed until after char_dev object is freed. To achieve this allow setting a "parent" device for character devices and pin them when doing cdev_add() and unpin when last reference to cdev structure is being released. Signed-off-by: Dmitry Torokhov --- Sorry, messed up the first attempt to send... So, how about these 2? I enabled kmemleak and added some debug printks and it looks like we dropping references and freeing object at right times and in proper order. Thanks! fs/char_dev.c | 18 +++++++++++++++++- include/linux/cdev.h | 1 + 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/fs/char_dev.c b/fs/char_dev.c index 3f152b9..f8c44cc 100644 --- a/fs/char_dev.c +++ b/fs/char_dev.c @@ -471,9 +471,19 @@ static int exact_lock(dev_t dev, void *data) */ int cdev_add(struct cdev *p, dev_t dev, unsigned count) { + int error; + p->dev = dev; p->count = count; - return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p); + + error = kobj_map(cdev_map, dev, count, NULL, + exact_match, exact_lock, p); + if (error) + return error; + + get_device(p->parent); + + return 0; } static void cdev_unmap(dev_t dev, unsigned count) @@ -498,14 +508,20 @@ void cdev_del(struct cdev *p) static void cdev_default_release(struct kobject *kobj) { struct cdev *p = container_of(kobj, struct cdev, kobj); + struct device *parent = p->parent; + cdev_purge(p); + put_device(parent); } static void cdev_dynamic_release(struct kobject *kobj) { struct cdev *p = container_of(kobj, struct cdev, kobj); + struct device *parent = p->parent; + cdev_purge(p); kfree(p); + put_device(parent); } static struct kobj_type ktype_cdev_default = { diff --git a/include/linux/cdev.h b/include/linux/cdev.h index fb45919..eba8251 100644 --- a/include/linux/cdev.h +++ b/include/linux/cdev.h @@ -12,6 +12,7 @@ struct module; struct cdev { struct kobject kobj; struct module *owner; + struct device *parent; const struct file_operations *ops; struct list_head list; dev_t dev; -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/