linux-kernel - Re: [PATCH] media: omap3isp: Shuffle cacheflush.h and include mm.h

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Date:   Wed, 27 May 2020 09:02:51 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Christoph Hellwig <hch@....de>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        Linux-sh list <linux-sh@...r.kernel.org>,
        Roman Zippel <zippel@...ux-m68k.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        linux-riscv@...ts.infradead.org,
        Linux-Arch <linux-arch@...r.kernel.org>,
        linux-c6x-dev@...ux-c6x.org,
        "open list:QUALCOMM HEXAGON..." <linux-hexagon@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "open list:TENSILICA XTENSA PORT (xtensa)" 
        <linux-xtensa@...ux-xtensa.org>, Arnd Bergmann <arnd@...db.de>,
        alpha <linux-alpha@...r.kernel.org>,
        linux-um <linux-um@...ts.infradead.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Openrisc <openrisc@...ts.librecores.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Michal Simek <monstr@...str.eu>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jessica Yu <jeyu@...nel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH] media: omap3isp: Shuffle cacheflush.h and include mm.h

Hi Nathan,

CC Laurent

On Wed, May 27, 2020 at 6:37 AM Nathan Chancellor
<natechancellor@...il.com> wrote:
> After mm.h was removed from the asm-generic version of cacheflush.h,
> s390 allyesconfig shows several warnings of the following nature:
>
> In file included from ./arch/s390/include/generated/asm/cacheflush.h:1,
>                  from drivers/media/platform/omap3isp/isp.c:42:
> ./include/asm-generic/cacheflush.h:16:42: warning: 'struct mm_struct'
> declared inside parameter list will not be visible outside of this
> definition or declaration
>
> cacheflush.h does not include mm.h nor does it include any forward
> declaration of these structures hence the warning. To avoid this,
> include mm.h explicitly in this file and shuffle cacheflush.h below it.
>
> Fixes: 19c0054597a0 ("asm-generic: don't include <linux/mm.h> in cacheflush.h")
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>

Thanks for your patch!

> I am aware the fixes tag is kind of irrelevant because that SHA will
> change in the next linux-next revision and this will probably get folded
> into the original patch anyways but still.
>
> The other solution would be to add forward declarations of these structs
> to the top of cacheflush.h, I just chose to do what Christoph did in the
> original patch. I am happy to do that instead if you all feel that is
> better.

That actually looks like a better solution to me, as it would address the
problem for all users.

>  drivers/media/platform/omap3isp/isp.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/omap3isp/isp.c b/drivers/media/platform/omap3isp/isp.c
> index a4ee6b86663e..54106a768e54 100644
> --- a/drivers/media/platform/omap3isp/isp.c
> +++ b/drivers/media/platform/omap3isp/isp.c
> @@ -39,8 +39,6 @@
>   *     Troy Laramy <t-laramy@...com>
>   */
>
> -#include <asm/cacheflush.h>
> -
>  #include <linux/clk.h>
>  #include <linux/clkdev.h>
>  #include <linux/delay.h>
> @@ -49,6 +47,7 @@
>  #include <linux/i2c.h>
>  #include <linux/interrupt.h>
>  #include <linux/mfd/syscon.h>
> +#include <linux/mm.h>
>  #include <linux/module.h>
>  #include <linux/omap-iommu.h>
>  #include <linux/platform_device.h>
> @@ -58,6 +57,8 @@
>  #include <linux/sched.h>
>  #include <linux/vmalloc.h>
>
> +#include <asm/cacheflush.h>
> +
>  #ifdef CONFIG_ARM_DMA_USE_IOMMU
>  #include <asm/dma-iommu.h>
>  #endif

Why does this file need <asm/cacheflush.h> at all?
It doesn't call any of the flush_*() functions, and seems to compile fine
without (on arm32).

Perhaps it was included at the top intentionally, to override the definitions
of copy_{to,from}_user_page()? Fortunately that doesn't seem to be the
case, from a quick look at the assembler output.

So let's just remove the #include instead?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds