Re: [PATCH v7 2/2] media: V3s: Add support for Allwinner CSI.

From: Yong <yong.deng@magewell.com>
To: 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
Subject: Re: [PATCH v7 2/2] media: V3s: Add support for Allwinner CSI.
Date: Tue, 30 Jan 2018 10:48:33 +0800	[thread overview]
Message-ID: <20180130104833.a06e44c558c7ddc6b38e20b3@magewell.com> (raw)
In-Reply-To: <c86097d7-dade-01e5-3826-3f22f9ca4b4f@infradead.org>

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.

> 
> > 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