Re: [PATCH v3 01/11] media: dt-bindings: ov772x: add device tree binding

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Mita-san,

On Thursday, 26 April 2018 19:17:55 EEST Akinobu Mita wrote:
> 2018-04-26 7:40 GMT+09:00 Laurent Pinchart:
> > On Wednesday, 25 April 2018 19:19:11 EEST Akinobu Mita wrote:
> >> 2018-04-24 0:54 GMT+09:00 Akinobu Mita <akinobu.mita@gmail.com>:
> >> > 2018-04-23 18:17 GMT+09:00 Laurent Pinchart:
> >> >> On Sunday, 22 April 2018 18:56:07 EEST Akinobu Mita wrote:
> >> >>> This adds a device tree binding documentation for OV7720/OV7725
> >> >>> sensor.
> >> >>> 
> >> >>> Cc: Jacopo Mondi <jacopo+renesas@jmondi.org>
> >> >>> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >> >>> Cc: Hans Verkuil <hans.verkuil@cisco.com>
> >> >>> Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
> >> >>> Cc: Mauro Carvalho Chehab <mchehab@s-opensource.com>
> >> >>> Cc: Rob Herring <robh+dt@kernel.org>
> >> >>> Reviewed-by: Rob Herring <robh@kernel.org>
> >> >>> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
> >> >>> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> >> >>> ---
> >> >>> * v3
> >> >>> - Add Reviewed-by: lines
> >> >>> 
> >> >>>  .../devicetree/bindings/media/i2c/ov772x.txt       | 42
> >> >>>  +++++++++++++++
> >> >>>  MAINTAINERS                                        |  1 +
> >> >>>  2 files changed, 43 insertions(+)
> >> >>>  create mode 100644
> >> >>>  Documentation/devicetree/bindings/media/i2c/ov772x.txt
> >> >>> 
> >> >>> diff --git a/Documentation/devicetree/bindings/media/i2c/ov772x.txt
> >> >>> b/Documentation/devicetree/bindings/media/i2c/ov772x.txt new file
> >> >>> mode
> >> >>> 100644
> >> >>> index 0000000..b045503
> >> >>> --- /dev/null
> >> >>> +++ b/Documentation/devicetree/bindings/media/i2c/ov772x.txt
> >> >>> @@ -0,0 +1,42 @@
> >> >>> +* Omnivision OV7720/OV7725 CMOS sensor
> >> >>> +
> >> >>> +The Omnivision OV7720/OV7725 sensor supports multiple resolutions
> >> >>> output,
> >> >>> +such as VGA, QVGA, and any size scaling down from CIF to 40x30. It
> >> >>> also
> >> >>> can +support the YUV422, RGB565/555/444, GRB422 or raw RGB output
> >> >>> formats. +
> >> >>> +Required Properties:
> >> >>> +- compatible: shall be one of
> >> >>> +     "ovti,ov7720"
> >> >>> +     "ovti,ov7725"
> >> >>> +- clocks: reference to the xclk input clock.
> >> >>> +- clock-names: shall be "xclk".
> >> >> 
> >> >> As there's a single clock we could omit clock-names, couldn't we ?
> >> > 
> >> > Sounds good.
> >> > 
> >> > I'll prepare another patch that replaces the clock consumer ID argument
> >> > of clk_get() from "xclk" to NULL, and remove the above line in this
> >> > bindings.
> >> 
> >> I thought it's easy to do.  However, there is a non-DT user
> >> (arch/sh/boards/mach-migor/setup.c) that defines a clock with "xclk" ID.
> >> 
> >> This can be resolved by retrying clk_get() with NULL if no entry
> >> with "xclk".  But should we do so or leave as is?
> > 
> > How about patching the board code to register the clock alias with
> > 
> >         clk_add_alias(NULL, "0-0021", "video_clk", NULL);
> 
> Sounds good.
> 
> But I'm a bit worried about whether clk_add_alias() can be called with
> alias == NULL.  I couldn't find such use case.

There aren't many occurrences, but

$ find . -type f -exec grep -l 'clk_add_alias(NULL' {} \;
/drivers/clk/ti/clk.c
/drivers/clk/ti/fixed-factor.c
/drivers/clk/ti/clk-dra7-atl.c
/drivers/clk/ti/composite.c

A quick code analysis also shows me that this should be supported.

> Probably Jacopo can verify whether it works or not with v4 patchset.

-- 
Regards,

Laurent Pinchart