Return-Path: Received: from mail.kernel.org ([198.145.29.99]:48418 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731870AbeLTOJz (ORCPT ); Thu, 20 Dec 2018 09:09:55 -0500 Date: Thu, 20 Dec 2018 15:09:51 +0100 From: Greg KH To: Buland Singh Cc: clemens@ladisch.de, arnd@arndb.de, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] hpet: Fix missing '=' character in the __setup() code of hpet_mmap_enable Message-ID: <20181220140951.GB8621@kroah.com> References: <20181220120524.30732-1-bsingh@redhat.com> <20181220122932.GB17138@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: stable-owner@vger.kernel.org List-ID: On Thu, Dec 20, 2018 at 07:12:55PM +0530, Buland Singh wrote: > On 12/20/18 5:59 PM, Greg KH wrote: > > On Thu, Dec 20, 2018 at 05:35:24PM +0530, Buland Singh wrote: > > > Commit '3d035f580699 ("drivers/char/hpet.c: allow user controlled mmap for > > > user processes")' introduced a new kernel command line parameter hpet_mmap, > > > that is required to expose the memory map of the HPET registers to > > > user-space. Unfortunately the kernel command line parameter 'hpet_mmap' is > > > broken and never takes effect due to missing '=' character in the __setup() > > > code of hpet_mmap_enable. > > > > > > Before this patch: > > > > > > dmesg output with the kernel command line parameter hpet_mmap=1 > > > > > > [ 0.204152] HPET mmap disabled > > > > > > dmesg output with the kernel command line parameter hpet_mmap=0 > > > > > > [ 0.204192] HPET mmap disabled > > > > > > After this patch: > > > > > > dmesg output with the kernel command line parameter hpet_mmap=1 > > > > > > [ 0.203945] HPET mmap enabled > > > > > > dmesg output with the kernel command line parameter hpet_mmap=0 > > > > > > [ 0.204652] HPET mmap disabled > > > > > > Fixes: 3d035f580699 ("drivers/char/hpet.c: allow user controlled mmap for user processes") > > > Signed-off-by: Buland Singh > > > --- > > > drivers/char/hpet.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c > > > index 4a22b4b41aef..9bffcd37cc7b 100644 > > > --- a/drivers/char/hpet.c > > > +++ b/drivers/char/hpet.c > > > @@ -377,7 +377,7 @@ static __init int hpet_mmap_enable(char *str) > > > pr_info("HPET mmap %s\n", hpet_mmap_enabled ? "enabled" : "disabled"); > > > return 1; > > > } > > > -__setup("hpet_mmap", hpet_mmap_enable); > > > +__setup("hpet_mmap=", hpet_mmap_enable); > > Hello Greag, > > > This has _never_ worked? Since 3.13? > > Yes, that's true :) > > > Why not just remove the thing as it is obvious no one actually has ever used it. > That would make the code even simpler :) > > Data Plane Development Kit (DPDK)[1] provides API that requires the CONFIG_HPET_MMAP > kernel configuration option to be enabled[2]. Some end users might want to use the > HPET MMAP functionality within the application. But, obviously, they really don't need to do that from the kernel command line as no one has ever noticed this didn't work :) Also, that page: > [2] https://doc.dpdk.org/guides-18.08/linux_gsg/enable_func.html Does not say to use this command line option either. So if no one has ever used it, please, let us just delete it. thanks, greg k-h