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

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Date:	Tue, 9 Dec 2014 14:41:00 +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 02:50 PM, Lee Jones wrote:
> >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.
> >
> 
> V4L2 driver wraps LED driver. This way the LED device can be
> controlled with use of two interfaces - LED subsystem sysfs
> and V4L2 Flash. This is the aim of the whole patch set.
> 
> I've thought it over again and it seems that I will need to cache
> somewhere these sub_nodes pointers. They have to be easily accessible
> for the V4L2 sub-device as it can be asynchronously registered
> or unregistered within V4L2 media device. Sub-devices are matched
> basing on the sub-node phandle.

Not quite getting this.  Can you explain this in another way please?

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