linux-kernel - Re: [PATCH 2/2] extcon: gpio: Add dt support for the driver.

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Date:	Thu, 19 Jun 2014 09:00:27 +0530
From:	George Cherian <george.cherian@...com>
To:	Mark Rutland <mark.rutland@....com>
CC:	"cw00.choi@...sung.com" <cw00.choi@...sung.com>,
	"myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"rdunlap@...radead.org" <rdunlap@...radead.org>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	"linux@...ck-us.net" <linux@...ck-us.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/2] extcon: gpio: Add dt support for the driver.

On 6/17/2014 9:27 PM, Mark Rutland wrote:
> On Tue, Jun 17, 2014 at 04:58:20AM +0100, George Cherian wrote:
>> Add device tree support to extcon-gpio driver.
>> Add devicetree binding documentation
>>
>> Signed-off-by: George Cherian <george.cherian@...com>
>> ---
>>   .../devicetree/bindings/extcon/extcon-gpio.txt     | 34 ++++++++++++++++++++++
>>   drivers/extcon/extcon-gpio.c                       | 29 ++++++++++++++++++
>>   2 files changed, 63 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/extcon/extcon-gpio.txt
>>
>> diff --git a/Documentation/devicetree/bindings/extcon/extcon-gpio.txt b/Documentation/devicetree/bindings/extcon/extcon-gpio.txt
>> new file mode 100644
>> index 0000000..80b791b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/extcon/extcon-gpio.txt
>> @@ -0,0 +1,34 @@
>> +GPIO based EXTCON
>> +
>> +EXTCON GPIO
>> +-----------
>> +
>> +Required Properties:
>> + - compatible: should be:
>> +   * "ti,extcon-gpio"
>> + - gpios: specifies the gpio pin used.
>> + - debounce: Debounce time for GPIO IRQ in ms
>> + - irq-flags: IRQ flag to be used ( eg: IRQ_TYPE_EDGE_FALLING)
> This looks distinctly odd. Why do you need this here?
The driver takes this as part of platform data. It never continues 
operation if
an invalid irq-flag is supplied. Also these can be used for different SoC's
whose GPIO's might support IRQ_TYPE_EDGE_FALLING/RISING.
Now since this is based on gpio we cant up front give a seperate
"interrupts = " property, since we dont know the gpio-pin irq number.

Chanwoo any comments?
>
>> +Optional Properties:
>> + - gpio-active-low: Property describing whether gpio active state is 1 or 0
>> +		    If defined , low state of gpio means active.
> Surely this is defined in the gpio flags?

Yes, I will make necessary changes.
>
>> + - check-on-resume: Property describing whether to check the gpio state
>> +		    while resuming from SLEEP.
> Does this need to be in DT? Surely we could jsut always check this?
okay. For my use-case I dont need this.
Chanwoo, any comments?
>> + - state-on: print_state is overriden with state_on string if provided.
>> +	     If NULL, default method of extcon class is used.
>> + - state_off: print_state is overriden with state_off string  if provided.
>> +	      If NUll, default method of extcon class is used.
> This means nothing from a HW perspective. This describes linux internal
> details.
You mean to say this should not be part of dt?

> [...]
>
>> +		of_property_read_u32(np, "debounce", (u32 *)&pdata->debounce);
>> +		of_property_read_u32(np, "irq-flags", (u32 *)&pdata->irq_flags);
> If you need theses casts, the code is broken.
I dont need this, will remove in v2.
>
> These functions can only read into a u32. If you pass a smaller type
> you'll trash aribtrary memory locations, and if you pass a larger type
> this is broken for BE.
true.
> Mark.


-- 
-George

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