linux-kernel - Re: [PATCH] i2c: sh_mobile: I2C_SH_MOBILE should depend on HAS

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Date:	Wed, 17 Dec 2014 09:47:47 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	Linux I2C <linux-i2c@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: sh_mobile: I2C_SH_MOBILE should depend on HAS_DMA

Hi Wolfram,

On Wed, Dec 17, 2014 at 9:39 AM, Wolfram Sang <wsa@...-dreams.de> wrote:
> On Wed, Dec 17, 2014 at 09:04:52AM +0100, Geert Uytterhoeven wrote:
>> On Wed, Dec 17, 2014 at 7:58 AM, Wolfram Sang <wsa@...-dreams.de> wrote:
>> > On Mon, Dec 15, 2014 at 02:37:04PM +0100, Geert Uytterhoeven wrote:
>> >> If NO_DMA=y:
>> >>
>> >> drivers/built-in.o: In function `sh_mobile_i2c_dma_unmap':
>> >> i2c-sh_mobile.c:(.text+0x60de42): undefined reference to `dma_unmap_single'
>> >> drivers/built-in.o: In function `sh_mobile_i2c_xfer_dma':
>> >> i2c-sh_mobile.c:(.text+0x60df22): undefined reference to `dma_map_single'
>> >> i2c-sh_mobile.c:(.text+0x60df2e): undefined reference to `dma_mapping_error'
>> >>
>> >> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>> >
>> > Thanks for spotting this. However, since DMA is opt-in, isn't this
>> > dependency too much? I can't think of anything better than #ifdeffing
>> > the code, though.
>>
>> You're right.
>>
>> E.g. drivers/spi/spi.c (in SPI the mapping is handled by the core), this
>> code is #ifdefed out.
>
> Then again, we could depend on ARM || SUPERH || (COMPILE_TEST &&
> HAS_DMA) to skip the #ifdeffery? ARM and SUPERH don't have NO_DMA.

If ARM and SUPERH imply HAS_DMA, that formula is almost identical to
the one I proposed in my patch?

       depends on HAS_DMA
       depends on SUPERH || ARCH_SHMOBILE || COMPILE_TEST

I just prefer to split dependencies in two lines where it makes sense ("hard"
dependencies vs. "soft" (user platform configuration) dependencies).

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
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