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Subject: Re: [PATCH v7 2/2] media: V3s: Add support for Allwinner CSI.
To:     Yong <yong.deng@magewell.com>, Randy Dunlap <rdunlap@infradead.org>
Cc:     Maxime Ripard <maxime.ripard@free-electrons.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Chen-Yu Tsai <wens@csie.org>,
        "David S. Miller" <davem@davemloft.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Stanimir Varbanov <stanimir.varbanov@linaro.org>,
        Hugues Fruchet <hugues.fruchet@st.com>,
        Yannick Fertre <yannick.fertre@st.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Arnd Bergmann <arnd@arndb.de>,
        Benjamin Gaignard <benjamin.gaignard@linaro.org>,
        Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Rick Chang <rick.chang@mediatek.com>,
        linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-sunxi@googlegroups.com
References: <1517217696-17816-1-git-send-email-yong.deng@magewell.com>
 <c86097d7-dade-01e5-3826-3f22f9ca4b4f@infradead.org>
 <20180130104833.a06e44c558c7ddc6b38e20b3@magewell.com>
From:   Hans Verkuil <hverkuil@xs4all.nl>
Message-ID: <ce3a30b9-f017-61b6-1fe6-f5dcc8bd3ec3@xs4all.nl>
Date:   Mon, 26 Feb 2018 12:06:37 +0100
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Hi all,

On 01/30/2018 03:48 AM, Yong wrote:
> Hi,
> 
> On Mon, 29 Jan 2018 13:49:14 -0800
> Randy Dunlap <rdunlap@infradead.org> wrote:
> 
>> On 01/29/2018 01:21 AM, Yong Deng wrote:
>>> Allwinner V3s SoC features two CSI module. CSI0 is used for MIPI CSI-2
>>> interface and CSI1 is used for parallel interface. This is not
>>> documented in datasheet but by test and guess.
>>>
>>> This patch implement a v4l2 framework driver for it.
>>>
>>> Currently, the driver only support the parallel interface. MIPI-CSI2,
>>> ISP's support are not included in this patch.
>>>
>>> Tested-by: Maxime Ripard <maxime.ripard@free-electrons.com>
>>> Signed-off-by: Yong Deng <yong.deng@magewell.com>
>>> ---
>>
>>
>> A previous version (I think v6) had a build error with the use of
>> PHYS_OFFSET, so Kconfig was modified to depend on ARM and ARCH_SUNXI
>> (one of which seems to be overkill).  As is here, the COMPILE_TEST piece is
>> meaningless for all arches except ARM.  If you care enough for COMPILE_TEST
>> (and I would), then you could make COMPILE_TEST useful on any arch by
>> removing the "depends on ARM" (the ARCH_SUNXI takes care of that) and by
>> having an alternate value for PHYS_OFFSET, like so:
>>
>> +#if defined(CONFIG_COMPILE_TEST) && !defined(PHYS_OFFSET)
>> +#define PHYS_OFFSET	0
>> +#endif
>>
>> With those 2 changes, the driver builds for me on x86_64.
> 
> I have considered this method.
> But it's so sick to put these code in dirver (for my own). I mean 
> this is meaningless for the driver itself and make people confused.
> 
> I grepped the driver/ code and I found many drivers writing Kconfig
> like this. For example:
> ARM && COMPILE_TEST
> MIPS && COMPILE_TEST
> PPC64 && COMPILE_TEST
> 
> BTW, for my own, I do not care about COMPILE_TEST.

There was a discussion about this in the v6 patch, but it petered out.

I want to merge this driver, but I would very much prefer that this
compiles with COMPILE_TEST. So unless someone has a better solution, then
adding 'hack' that defines PHYS_OFFSET to 0 for COMPILE_TEST would be required.

Otherwise this driver looks good, so it is just this issue blocking it.

Regards,

	Hans

> 
>>
>>> diff --git a/drivers/media/platform/sunxi/sun6i-csi/Kconfig b/drivers/media/platform/sunxi/sun6i-csi/Kconfig
>>> new file mode 100644
>>> index 0000000..f80c965
>>> --- /dev/null
>>> +++ b/drivers/media/platform/sunxi/sun6i-csi/Kconfig
>>> @@ -0,0 +1,10 @@
>>> +config VIDEO_SUN6I_CSI
>>> +	tristate "Allwinner V3s Camera Sensor Interface driver"
>>> +	depends on ARM
>>> +	depends on VIDEO_V4L2 && COMMON_CLK && VIDEO_V4L2_SUBDEV_API && HAS_DMA
>>> +	depends on ARCH_SUNXI || COMPILE_TEST
>>> +	select VIDEOBUF2_DMA_CONTIG
>>> +	select REGMAP_MMIO
>>> +	select V4L2_FWNODE
>>> +	---help---
>>> +	   Support for the Allwinner Camera Sensor Interface Controller on V3s.
>>
>> thanks,
>> -- 
>> ~Randy
> 
> 
> Thanks,
> Yong
>