From: "Eads, Gage" <gage.eads@intel.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"arnd@arndb.de" <arnd@arndb.de>,
"Karlsson, Magnus" <magnus.karlsson@intel.com>,
"Topel, Bjorn" <bjorn.topel@intel.com>
Subject: RE: [PATCH 01/20] dlb2: add skeleton for DLB 2.0 driver
Date: Fri, 24 Jul 2020 21:00:20 +0000 [thread overview]
Message-ID: <DM6PR11MB2572EB1152A0B1453531D72BF6770@DM6PR11MB2572.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20200720191903.GD1529125@kroah.com>
> -----Original Message-----
> From: Greg KH <gregkh@linuxfoundation.org>
> Sent: Monday, July 20, 2020 2:19 PM
> To: Eads, Gage <gage.eads@intel.com>
> Cc: linux-kernel@vger.kernel.org; arnd@arndb.de; Karlsson, Magnus
> <magnus.karlsson@intel.com>; Topel, Bjorn <bjorn.topel@intel.com>
> Subject: Re: [PATCH 01/20] dlb2: add skeleton for DLB 2.0 driver
>
> On Mon, Jul 20, 2020 at 07:02:05PM +0000, Eads, Gage wrote:
> >
> >
> > > -----Original Message-----
> > > From: Greg KH <gregkh@linuxfoundation.org>
> > > Sent: Saturday, July 18, 2020 1:47 AM
> > > To: Eads, Gage <gage.eads@intel.com>
> > > Cc: linux-kernel@vger.kernel.org; arnd@arndb.de; Karlsson, Magnus
> > > <magnus.karlsson@intel.com>; Topel, Bjorn <bjorn.topel@intel.com>
> > > Subject: Re: [PATCH 01/20] dlb2: add skeleton for DLB 2.0 driver
> > >
> > > On Fri, Jul 17, 2020 at 06:18:46PM +0000, Eads, Gage wrote:
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Greg KH <gregkh@linuxfoundation.org>
> > > > > Sent: Sunday, July 12, 2020 10:58 AM
> > > > > To: Eads, Gage <gage.eads@intel.com>
> > > > > Cc: linux-kernel@vger.kernel.org; arnd@arndb.de; Karlsson, Magnus
> > > > > <magnus.karlsson@intel.com>; Topel, Bjorn <bjorn.topel@intel.com>
> > > > > Subject: Re: [PATCH 01/20] dlb2: add skeleton for DLB 2.0 driver
> > > > >
> > > > > On Sun, Jul 12, 2020 at 08:43:12AM -0500, Gage Eads wrote:
> > > > > > +static int dlb2_probe(struct pci_dev *pdev,
> > > > > > + const struct pci_device_id *pdev_id) {
> > > > > > + struct dlb2_dev *dlb2_dev;
> > > > > > + int ret;
> > > > > > +
> > > > > > + dev_dbg(&pdev->dev, "probe\n");
> > > > >
> > > > > ftrace is your friend. Remove all of your debugging code now, you
> don't
> > > need
> > > > > it anymore, especially for stuff like this where you didn't even need it
> in
> > > the
> > > > > first place :(
> > > >
> > > > I'll remove this and other similar dev_dbg() calls. This was an oversight
> on
> > > my part.
> > > >
> > > > I have other instances that a kprobe can't easily replace, such as
> printing
> > > structure contents, that are useful for tracing the usage of the driver. It
> looks
> > > like other misc drivers use dev_dbg() similarly -- do you consider this an
> > > acceptable use of a debug print?
> > >
> > > Why can't a kernel tracepoint print a structure?
> >
> > I meant the command-line installed kprobes[1], but instrumenting the
> driver is
> > certainly an option. We don't require the much lower overhead of a
> tracepoint,
> > so I didn't choose it. This driver handles the (performance-insensitive)
> > device configuration, while the fast-path operations take place in user-
> space.
> >
> > Another reason is the "hardware access library" files use only non-GPL
> external
> > symbols, and some tracepoint functions are exported GPL. Though it's
> probably
> > feasible to lift that tracing code up into a (GPLv2-only) caller function.
>
> Stop going through crazy gyrations for something that your own legal
> team has told you not to do anymore in the first place.
>
> No "hardware access library" files please, that's not how Linux drivers
> are written.
>
> you all know better...
>
> > But if tracepoints are the preferred method and/or you think the driver
> would
> > benefit, I'll make the change.
>
> I don't think you need any of that stuff, now that the code works
> properly, right?
There are no known issues, correct. The logging (whether it's
dev_dbg/tracepoints/etc.) would be for user-space developers -- visibility into
the driver could help them debug issues in their own code.
It's hardly a critical feature; I'm happy to change or remove it if necessary.
But it could be helpful, isn't a maintenance burden or performance hindrance,
and (AFAICT) shouldn't pose any security risks.
Thanks,
Gage
>
> greg k-h
next prev parent reply other threads:[~2020-07-24 21:00 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-12 13:43 [PATCH 00/20] dlb2: introduce DLB 2.0 device driver Gage Eads
2020-07-12 13:43 ` [PATCH 01/20] dlb2: add skeleton for DLB 2.0 driver Gage Eads
2020-07-12 15:56 ` Greg KH
2020-07-17 18:19 ` Eads, Gage
2020-07-18 6:46 ` Greg KH
2020-07-12 15:58 ` Greg KH
2020-07-17 18:18 ` Eads, Gage
2020-07-18 6:46 ` Greg KH
2020-07-20 19:02 ` Eads, Gage
2020-07-20 19:19 ` Greg KH
2020-07-24 21:00 ` Eads, Gage [this message]
2020-07-12 13:43 ` [PATCH 02/20] dlb2: initialize PF device Gage Eads
2020-07-12 13:43 ` [PATCH 03/20] dlb2: add resource and device initialization Gage Eads
2020-07-12 13:43 ` [PATCH 04/20] dlb2: add device ioctl layer and first 4 ioctls Gage Eads
2020-07-12 14:42 ` Randy Dunlap
2020-07-17 18:20 ` Eads, Gage
2020-07-12 14:53 ` Randy Dunlap
2020-07-17 18:20 ` Eads, Gage
2020-07-12 15:28 ` Arnd Bergmann
2020-07-17 18:19 ` Eads, Gage
2020-07-17 18:56 ` Arnd Bergmann
2020-07-17 20:05 ` Eads, Gage
2020-07-18 6:48 ` gregkh
2020-08-04 22:20 ` Eads, Gage
2020-08-05 6:46 ` gregkh
2020-08-05 15:07 ` Eads, Gage
2020-08-05 15:17 ` gregkh
2020-08-05 15:39 ` Eads, Gage
2020-07-12 13:43 ` [PATCH 05/20] dlb2: add sched domain config and reset support Gage Eads
2020-07-12 13:43 ` [PATCH 06/20] dlb2: add ioctl to get sched domain fd Gage Eads
2020-07-12 13:43 ` [PATCH 07/20] dlb2: add runtime power-management support Gage Eads
2020-07-12 13:43 ` [PATCH 08/20] dlb2: add queue create and queue-depth-get ioctls Gage Eads
2020-07-12 13:43 ` [PATCH 09/20] dlb2: add ioctl to configure ports, query poll mode Gage Eads
2020-07-12 15:34 ` Arnd Bergmann
2020-07-17 18:19 ` Eads, Gage
2020-07-12 13:43 ` [PATCH 10/20] dlb2: add port mmap support Gage Eads
2020-07-12 13:43 ` [PATCH 11/20] dlb2: add start domain ioctl Gage Eads
2020-07-12 13:43 ` [PATCH 12/20] dlb2: add queue map and unmap ioctls Gage Eads
2020-07-12 13:43 ` [PATCH 13/20] dlb2: add port enable/disable ioctls Gage Eads
2020-07-12 13:43 ` [PATCH 14/20] dlb2: add CQ interrupt support Gage Eads
2020-07-12 13:43 ` [PATCH 15/20] dlb2: add domain alert support Gage Eads
2020-07-12 13:43 ` [PATCH 16/20] dlb2: add sequence-number management ioctls Gage Eads
2020-07-12 13:43 ` [PATCH 17/20] dlb2: add cos bandwidth get/set ioctls Gage Eads
2020-07-12 13:43 ` [PATCH 18/20] dlb2: add device FLR support Gage Eads
2020-07-12 13:43 ` [PATCH 19/20] dlb2: add basic PF sysfs interfaces Gage Eads
2020-07-12 13:43 ` [PATCH 20/20] dlb2: add ingress error handling Gage Eads
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