linux-kernel - Re: [PATCH/RFC v9 04/19] mfd: max77693: adjust max77693_led_platform

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Message-ID: <20141209135017.GY3951@x1>
Date:	Tue, 9 Dec 2014 13:50:17 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Jacek Anaszewski <j.anaszewski@...sung.com>
Cc:	linux-leds@...r.kernel.org, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, kyungmin.park@...sung.com,
	b.zolnierkie@...sung.com, pavel@....cz, cooloney@...il.com,
	rpurdie@...ys.net, sakari.ailus@....fi, s.nawrocki@...sung.com,
	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	Chanwoo Choi <cw00.choi@...sung.com>
Subject: Re: [PATCH/RFC v9 04/19] mfd: max77693: adjust
 max77693_led_platform_data

On Tue, 09 Dec 2014, Jacek Anaszewski wrote:

> On 12/09/2014 11:04 AM, Lee Jones wrote:
> >On Tue, 09 Dec 2014, Jacek Anaszewski wrote:
> >
> >>On 12/09/2014 09:50 AM, Lee Jones wrote:
> >>>On Wed, 03 Dec 2014, Jacek Anaszewski wrote:
> >>>
> >>>>Add "label" array for Device Tree strings with the name of a LED device
> >>>>and make flash_timeout a two element array, for caching the sub-led
> >>>>related flash timeout. Added is also an array for caching pointers to the
> >>>>sub-nodes representing sub-leds.
> >>>>
> >>>>Signed-off-by: Jacek Anaszewski <j.anaszewski@...sung.com>
> >>>>Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
> >>>>Cc: Chanwoo Choi <cw00.choi@...sung.com>
> >>>>Cc: Lee Jones <lee.jones@...aro.org>
> >>>>---
> >>>>  include/linux/mfd/max77693.h |    4 +++-
> >>>>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>>>
> >>>>diff --git a/include/linux/mfd/max77693.h b/include/linux/mfd/max77693.h
> >>>>index f0b6585..c80ee99 100644
> >>>>--- a/include/linux/mfd/max77693.h
> >>>>+++ b/include/linux/mfd/max77693.h
> >>>>@@ -88,16 +88,18 @@ enum max77693_led_boost_mode {
> >>>>  };
> >>>>
> >>>>  struct max77693_led_platform_data {
> >>>>+	const char *label[2];
> >>>>  	u32 fleds[2];
> >>>>  	u32 iout_torch[2];for_each_available_child_of_node
> >>>>  	u32 iout_flash[2];
> >>>>  	u32 trigger[2];
> >>>>  	u32 trigger_type[2];
> >>>>+	u32 flash_timeout[2];
> >>>>  	u32 num_leds;
> >>>>  	u32 boost_mode;
> >>>>-	u32 flash_timeout;
> >>>>  	u32 boost_vout;
> >>>>  	u32 low_vsys;
> >>>>+	struct device_node *sub_nodes[2];
> >>>
> >>>I haven't seen anyone do this before.  Why can't you use the provided
> >>>OF functions to traverse through your tree?
> >>
> >>I use for_each_available_child_of_node when parsing DT node, but I
> >>need to cache the pointer to sub-node to be able to use it later
> >>when it needs to be passed to V4L2 sub-device which is then
> >>asynchronously matched by the phandle to sub-node.
> >>
> >>If it is not well seen to cache it in the platform data then
> >>I will find different way to accomplish this.
> >
> >I haven't seen the end-driver for this, but why can't you use that
> >device's of_node pointer?
> 
> Maybe it is indeed a good idea. I could pass the of_node pointer
> and the sub-led identifier to the V4L2 sub-device and there look
> for the sub-node containing relevant identifier. The downside
> would be only that for_each_available_child_of_node would
> have to be called twice - in the led driver and in the V4L2 sub-device.
> I think that we can live with it.

Are the LED and V4L2 drivers children of this MFD?  If so, you can use
the of_compatible attribute in struct mfd_cell to populate the each
child's of_node dynamically i.e. the MFD core will do that for you.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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