From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: [RFC PATCH] phylib: mdio: handle register/unregister/register sequence Date: Thu, 22 Aug 2013 08:27:57 -0700 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 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 To: Boris BREZILLON Return-path: Content-Disposition: inline In-Reply-To: <1377174836-10569-1-git-send-email-b.brezillon@overkiz.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.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