linux-kernel - Re: [PATCH 0/2] Remove support for deprecated %pf and %pF in vsprintf

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Date:   Fri, 22 Mar 2019 15:53:50 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Petr Mladek <pmladek@...e.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        scsi <linux-scsi@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Linux MMC List <linux-mmc@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        linux-um@...ts.infradead.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-block@...r.kernel.org,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        linux-btrfs <linux-btrfs@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        xen-devel@...ts.xenproject.org,
        ceph-devel <ceph-devel@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Linux MM <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Lars Ellenberg <drbd-dev@...ts.linbit.com>
Subject: Re: [PATCH 0/2] Remove support for deprecated %pf and %pF in vsprintf

Hi Geert,

On Fri, Mar 22, 2019 at 02:37:18PM +0100, Geert Uytterhoeven wrote:
> Hi Sakari,
> 
> On Fri, Mar 22, 2019 at 2:25 PM Sakari Ailus
> <sakari.ailus@...ux.intel.com> wrote:
> > The printk family of functions supports %ps and %pS conversion specifiers
> > to print function names. Yet the deprecated %pf and %pF conversion
> > specifiers with equivalent functionality remain supported. A number of
> > users of %pf and %pF remain.
> >
> > This patchsets converts the existing users of %pf and %pF to %ps and %pS,
> > respectively, and removes support for the deprecated %pf and %pF.
> >
> > The patches apply cleanly both on 5.1-rc1 as well as on Linux-next. No new
> > %pf or %pF users have been added in the meantime so the patch is
> > sufficient as itself on linux-next, too.
> 
> Do you know in which commit they became deprecated, so the backporters
> know how far this can be backported safely?

That appears to be 04b8eb7a4ccd
("symbol lookup: introduce dereference_symbol_descriptor()"), the same
patch that made %p[fF] and %p[sS] functionally equivalent.

But my personal opinion would be not to backport the patch for two reasons:
the sheer number of files it touches (those format strings change for
various reasons) and the meager benefits it has on older kernels as any
backported patch using %s or %S still works as such. Porting a patch
forward should have no issues either as checkpatch.pl has been complaining
of the use of %pf and %pF for a while now.

-- 
Kind regards,

Sakari Ailus
sakari.ailus@...ux.intel.com