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From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
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Subject: Re: [PATCH v3 12/20] media: Remove depends on HAS_DMA in case of platform dependency
Date: Mon, 7 May 2018 09:21:47 +0200	[thread overview]
Message-ID: <CAMuHMdXp8u9O7Yt3W+WxuOOadYOM+_28DLOMfktwgy_WqML_0A@mail.gmail.com> (raw)
In-Reply-To: <20180505094743.4d201ba0@vento.lan>

Hi Mauro,

On Sat, May 5, 2018 at 2:47 PM, Mauro Carvalho Chehab
<mchehab+samsung@kernel.org> wrote:
> Em Tue, 17 Apr 2018 19:49:12 +0200
> Geert Uytterhoeven <geert@linux-m68k.org> escreveu:
>
>> Remove dependencies on HAS_DMA where a Kconfig symbol depends on another
>> symbol that implies HAS_DMA, and, optionally, on "|| COMPILE_TEST".
>
> Applying a patch like that is hard, as there are lots of churn at
> the code. That's against latest media upstream:

[...]

I can rebase. What's your preferred target? media-next?

>> In most cases this other symbol is an architecture or platform specific
>> symbol, or PCI.
>>
>> Generic symbols and drivers without platform dependencies keep their
>> dependencies on HAS_DMA, to prevent compiling subsystems or drivers that
>> cannot work anyway.
>
> Actually, depends on HAS_DMA was introduced on media because builds
> were failing otherwise. We started adding it before the addition
> of COMPILE_TEST.

Indeed. Before the 5 commits below, a missing dependency on HAS_DMA
would cause the build to fail for NO_DMA platforms.

    f29ab49b5388b2f8 dma-mapping: Convert NO_DMA get_dma_ops() into a real dummy
    ab642e952f80c66c dma-coherent: Add NO_DMA dummies for managed DMA API
    c1ce6c2beea38171 mm: Add NO_DMA dummies for DMA pool API
    bff739b6559e2fce scsi: Add NO_DMA dummies for SCSI DMA mapping API
    1f674e16f9ce6eb2 usb: gadget: Add NO_DMA dummies for DMA mapping API

> Can we just remove all HAS_DMA Kconfig dependencies as a hole from the
> entire media subsystem, with something like:
>
>         $ for i in $(find drivers/media -name Kconfig) $(find drivers/staging/media -name Kconfig); do sed '/depends on HAS_DMA/d;s/ && HAS_DMA//g' -i $i; done
>
> Or would it cause build issues?

It should not cause build issues, but it would enable lots of drivers that
need DMA platform support on platforms where they wouldn't work, making the
life of distro configurators harder.

That's why my series removes HAS_DMA only for symbols that have a platform
dependency.

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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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  reply	other threads:[~2018-05-07  7:21 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-17 17:49 [PATCH v3 00/20] Allow compile-testing NO_DMA (drivers) Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 01/20] ASoC: Remove depends on HAS_DMA in case of platform dependency Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 02/20] ata: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 03/20] crypto: " Geert Uytterhoeven
2018-04-28  8:24   ` Herbert Xu
2018-04-17 17:49 ` [PATCH v3 04/20] fbdev: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 05/20] firewire: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 06/20] fpga: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 07/20] i2c: " Geert Uytterhoeven
2018-04-18  7:01   ` Wolfram Sang
2018-04-17 17:49 ` [PATCH v3 08/20] iio: adc: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 09/20] iommu: " Geert Uytterhoeven
2018-05-03 13:02   ` Joerg Roedel
2018-04-17 17:49 ` [PATCH v3 10/20] lightnvm: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 11/20] mailbox: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 12/20] media: " Geert Uytterhoeven
2018-05-05 12:47   ` Mauro Carvalho Chehab
2018-05-07  7:21     ` Geert Uytterhoeven [this message]
2018-04-17 17:49 ` [PATCH v3 13/20] mmc: " Geert Uytterhoeven
2018-04-19 13:17   ` Ulf Hansson
2018-04-17 17:49 ` [PATCH v3 14/20] mtd: " Geert Uytterhoeven
2018-04-22 17:12   ` Boris Brezillon
2018-04-17 17:49 ` [PATCH v3 15/20] net: " Geert Uytterhoeven
2018-04-19 16:41   ` Kalle Valo
2018-04-17 17:49 ` [PATCH v3 16/20] remoteproc: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 17/20] serial: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 18/20] spi: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 19/20] staging: vc04_services: " Geert Uytterhoeven
2018-04-17 17:49 ` [PATCH v3 20/20] usb: " Geert Uytterhoeven

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