From: Greg KH <gregkh@linuxfoundation.org>
To: Buland Singh <bsingh@redhat.com>
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
Date: Thu, 20 Dec 2018 15:09:51 +0100 [thread overview]
Message-ID: <20181220140951.GB8621@kroah.com> (raw)
In-Reply-To: <a9704df4-53ee-5b12-2ab1-477fb7e8f083@redhat.com>
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 <bsingh@redhat.com>
> > > ---
> > > 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
next prev parent reply other threads:[~2018-12-20 14:09 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-20 12:05 [PATCH v2] hpet: Fix missing '=' character in the __setup() code of hpet_mmap_enable Buland Singh
2018-12-20 12:29 ` Greg KH
2018-12-20 13:42 ` Buland Singh
2018-12-20 14:09 ` Greg KH [this message]
2018-12-21 12:18 ` Buland Singh
2018-12-21 12:46 ` Greg KH
2019-01-06 14:09 ` Buland Singh
2019-01-07 12:34 ` Prarit Bhargava
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