linux-kernel - Re: [PATCH v3 14/17] PCI: dwc: artpec6: Add support for endpoint mode

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Date:   Fri, 3 Nov 2017 15:16:20 +0100
From:   Niklas Cassel <niklas.cassel@...s.com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Jesper Nilsson <jespern@...s.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Jingoo Han <jingoohan1@...il.com>,
        Shawn Guo <shawn.guo@...aro.org>,
        Peter Robinson <pbrobinson@...il.com>,
        Xiaowei Song <songxiaowei@...ilicon.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...s.com>
Subject: Re: [PATCH v3 14/17] PCI: dwc: artpec6: Add support for endpoint mode

On 11/03/2017 11:23 AM, Arnd Bergmann wrote:
> On Fri, Nov 3, 2017 at 10:56 AM, Niklas Cassel <niklas.cassel@...s.com> wrote:
>> On 11/02/2017 10:13 AM, Arnd Bergmann wrote:

> What I meant is that you can remove the #ifdef entirely if you add
> 
>          if (!IS_ENABLED(CONFIG_PCIE_ARTPEC6_HOST))
>                   return -ENODEV;
> 
> to artpec6_pcie_probe(). Anything after that statement will get
> silently dropped by the compiler, including static functions and
> structures that are referenced indirectly from there.

Wow, this actually helps gcc with dead code elimination.
It was even possible to add those !IS_ENABLED the two different
case labels in the switch statement.
I get no unwanted symbols when looking at the vmlinux in gdb.

Great suggestion Arnd :)


Regards,
Niklas