From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregkh@linuxfoundation.org (Greg Kroah-Hartman) Date: Thu, 22 Aug 2013 08:27:57 -0700 Subject: [RFC PATCH] phylib: mdio: handle register/unregister/register sequence In-Reply-To: <1377174836-10569-1-git-send-email-b.brezillon@overkiz.com> References: <1377174836-10569-1-git-send-email-b.brezillon@overkiz.com> Message-ID: <20130822152757.GA23163@kroah.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Aug 22, 2013 at 02:33:56PM +0200, Boris BREZILLON wrote: > Hello, > > This patch is a proposal to support the register/unregister/register > sequence on a given mdio bus. > > I use the register/unregister/register sequence to add a fallback when the > of_mdiobus_register (this function calls mdiobus_register with phy_mask > set to ~0) does not register any phy device (because the device tree does > not define any phy). > In this case I call mdiobus_unregister and then call mdiobus_register with > a phy_mask set to 0 to trigger a full mdio bus scan. > > I'm not sure this is the right way to do it (this is why I added RFC in the > subject). > > Could someone help me figuring out what I should use to implement my fallback ? > > 1) use the register/unregister/register sequence That will not work. Well, you might think it would work, but then things randomly start breaking later on. Try it with the KOBJECT_DELAYED_DESTROY build option in linux-next, and watch things go "boom" :) The rule is, you should never register a kobject/struct device that you have previously unregistered before, as you really don't know if unregistering has finished or not. sorry, greg k-h From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753134Ab3HVP0G (ORCPT ); Thu, 22 Aug 2013 11:26:06 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:43491 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752230Ab3HVP0E (ORCPT ); Thu, 22 Aug 2013 11:26:04 -0400 Date: Thu, 22 Aug 2013 08:27:57 -0700 From: Greg Kroah-Hartman To: Boris BREZILLON Cc: "David S. Miller" , Mark Brown , Nick Bowler , Grant Likely , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC PATCH] phylib: mdio: handle register/unregister/register sequence Message-ID: <20130822152757.GA23163@kroah.com> References: <1377174836-10569-1-git-send-email-b.brezillon@overkiz.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1377174836-10569-1-git-send-email-b.brezillon@overkiz.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 22, 2013 at 02:33:56PM +0200, Boris BREZILLON wrote: > Hello, > > This patch is a proposal to support the register/unregister/register > sequence on a given mdio bus. > > I use the register/unregister/register sequence to add a fallback when the > of_mdiobus_register (this function calls mdiobus_register with phy_mask > set to ~0) does not register any phy device (because the device tree does > not define any phy). > In this case I call mdiobus_unregister and then call mdiobus_register with > a phy_mask set to 0 to trigger a full mdio bus scan. > > I'm not sure this is the right way to do it (this is why I added RFC in the > subject). > > Could someone help me figuring out what I should use to implement my fallback ? > > 1) use the register/unregister/register sequence That will not work. Well, you might think it would work, but then things randomly start breaking later on. Try it with the KOBJECT_DELAYED_DESTROY build option in linux-next, and watch things go "boom" :) The rule is, you should never register a kobject/struct device that you have previously unregistered before, as you really don't know if unregistering has finished or not. sorry, greg k-h