From: Romain Perier Subject: Re: [PATCH 4/9] hwrng: omap - Use the managed device resource API for registration Date: Wed, 7 Sep 2016 16:23:53 +0200 Message-ID: <57D022F9.2020407@free-electrons.com> References: <20160906153857.5503-1-romain.perier@free-electrons.com> <20160906153857.5503-5-romain.perier@free-electrons.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: dsaxena@plexity.net, mpm@selenic.com, Herbert Xu , Gregory Clement , Thomas Petazzoni , Nadav Haklai , Omri Itach , Shadi Ammouri , Yahuda Yitschak , Hanna Hawa , Neta Zur Hershkovits , Igal Liberman , Marcin Wojtas , linux-crypto@vger.kernel.org To: PrasannaKumar Muralidharan Return-path: Received: from down.free-electrons.com ([37.187.137.238]:38751 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756118AbcIGOX4 (ORCPT ); Wed, 7 Sep 2016 10:23:56 -0400 In-Reply-To: Sender: linux-crypto-owner@vger.kernel.org List-ID: Hello, Le 06/09/2016 18:31, PrasannaKumar Muralidharan a écrit : >> Use devm_hwrng_register instead of hwrng_register. It avoids the need >> to handle unregistration explicitly from the remove function. >> >> Signed-off-by: Romain Perier >> --- >> drivers/char/hw_random/omap-rng.c | 4 +--- >> 1 file changed, 1 insertion(+), 3 deletions(-) >> >> diff --git a/drivers/char/hw_random/omap-rng.c b/drivers/char/hw_random/omap-rng.c >> index d47b24d..171c3e8 100644 >> --- a/drivers/char/hw_random/omap-rng.c >> +++ b/drivers/char/hw_random/omap-rng.c >> @@ -381,7 +381,7 @@ static int omap_rng_probe(struct platform_device *pdev) >> if (ret) >> goto err_ioremap; >> >> - ret = hwrng_register(&omap_rng_ops); >> + ret = devm_hwrng_register(dev, &omap_rng_ops); >> if (ret) >> goto err_register; >> >> @@ -402,8 +402,6 @@ static int omap_rng_remove(struct platform_device *pdev) >> { >> struct omap_rng_dev *priv = platform_get_drvdata(pdev); >> >> - hwrng_unregister(&omap_rng_ops); >> - >> priv->pdata->cleanup(priv); >> >> pm_runtime_put_sync(&pdev->dev); >> -- > > If devm_hwrng_register is used hwrng_unregister will be called after > pm_runtime_disable is called. If RNG device is in use calling > omap_rng_remove may not work properly. > The case where the remove function is called is if you unbind the driver by hand or you call rmmod while the RNG device is used. I don't think that the kernel will call platform->remove is the device is in use (so /dev/hwrng). I mean the argument that the unregister function is called after pm_runtime_disable is correct, but I don't think that the remove function might be called while the device is in use. There is necessarily a mutual exclusive case between "use the device" and "call the remove function of the device". However, I am open to suggestions. Regards, -- Romain Perier, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com