linux-kernel - Re: [PATCH] dmaengine: remove debugfs #ifdef

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Date:   Mon, 20 Sep 2021 19:28:01 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Hyun Kwon <hyun.kwon@...inx.com>, Vinod Koul <vkoul@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Sanjay R Mehta <sanju.mehta@....com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Arnd Bergmann <arnd@...db.de>,
        Jianqiang Chen <jianqiang.chen@...inx.com>,
        Quanyang Wang <quanyang.wang@...driver.com>,
        Yang Li <yang.lee@...ux.alibaba.com>,
        Allen Pais <apais@...ux.microsoft.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Biju Das <biju.das.jz@...renesas.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        dmaengine@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dmaengine: remove debugfs #ifdef

Hi Arnd,

On Mon, Sep 20, 2021 at 02:50:52PM +0200, Arnd Bergmann wrote:
> On Mon, Sep 20, 2021 at 2:47 PM Laurent Pinchart wrote:
> >
> > It's only a few bytes of data in struct dma_device, but a bit more in
> > .text here. Is the simplification really required in this driver ?
> 
> The intention was to not change the resulting object code in this driver,
> and I still don't see where it would grow after dead-code-elimination removes
> all the unused static functions. What am I missing?

Indeed, gcc does a fairly good job there. The .text section doesn't
grow. Interestingly, there's an increase in size in the .data and
.rodata sections in the xilinx-dpdma module:

-  8 .rodata.str1.8 0000029f  0000000000000000  0000000000000000  00003660  2**3
+  8 .rodata.str1.8 000002a7  0000000000000000  0000000000000000  00003660  2**3

- 10 .rodata       00001080  0000000000000000  0000000000000000  00003960  2**5
+ 10 .rodata       000010e0  0000000000000000  0000000000000000  00003960  2**5

- 15 .data         00001050  0000000000000000  0000000000000000  00004e40  2**5
+ 15 .data         00001090  0000000000000000  0000000000000000  00004ea0  2**5

I'm not entirely sure where it comes from, it may be related to
instrumentation caused by debugging options.

For your patch,

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

-- 
Regards,

Laurent Pinchart