gpio-led driver

From: raulpblooper@gmail.com (Raul Piper)
To: kernelnewbies@lists.kernelnewbies.org
Subject: gpio-led driver
Date: Thu, 28 Jul 2016 17:00:05 +0530	[thread overview]
Message-ID: <CAEwN+MAu17RikUpLGBiCBuKrfgLv5+9NSJXxO0kEzua4m6JeAQ@mail.gmail.com> (raw)
In-Reply-To: <57922F36.3010505@samsung.com>

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- kirkwood-ns2.dtb
This compiles fine.I was trying to compile only the "leds-ns2.dts"
file, not knowing the actual dtb was kirkwood-ns2.dtb .Thanks !!
This means I cant compile directly the files inside the
Documentation/bindings/leds/ .They have to be associated as some node
with some boards first .

On Fri, Jul 22, 2016 at 8:05 PM, Jacek Anaszewski
<j.anaszewski@samsung.com> wrote:
> On 07/22/2016 12:10 PM, Raul Piper wrote:
>>
>> On Thu, Jul 21, 2016 at 12:10 PM, Jacek Anaszewski
>> <j.anaszewski@samsung.com> wrote:
>>>
>>> Hi Raul,
>>>
>>> On 07/20/2016 01:17 PM, Raul Piper wrote:
>>>>
>>>>
>>>> Hi,
>>>> I wanted to know the part number for the leds-gpio.c in the
>>>> driver/leds folder and the device tree bindings for this driver .Can
>>>> some one point out to me where in Linux kernel it is?
>>>
>>>
>>>
>>> What do you mean by part number? This is generic driver for LEDs
>>> connected directly to a GPIO.
>>
>>
>> Understood,I thought there is some specific part number of the led
>> like all other led drivers in the same folder.
>>
>>> You can find DT documentation for it in the following location:
>>>
>>> Documentation/devicetree/bindings/leds/leds-gpio.txt
>>>
>>
>>   I tried compiling the sample dts file(leds-ns2.dts)  using the dtc
>> compiler .
>>
>> dtc -I dts -O dtb -o leds-ns2.dtb leds-ns2.dts
>>
>> but I am getting this error :
>>
>> DTC: dts->dtb  on file "leds-ns2.dts"
>> Error: leds-ns2.dts:1.1-2 syntax error
>> FATAL ERROR: Unable to parse input tree
>
>
> One minute of googling gives the answer:
>
> You can use the Makefile provided with the kernel:
>
> e.g.
>
> make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- kirkwood-ns2.dtb
>
> Make sure that CROSS_COMPILE matches your toolchain prefix.
>
>> Once it starts compiling fine I will modify it according to my
>> driver.Can I build the dtb and load it the way I load the kernel
>> driver.Do I have to do it before or after the insmod ?
>
>
> dtb is required to properly boot the system. It must be appended to the
> kernel image. You have to acquire some knowledge about bootloader
> present on your board and at what address it expects DT blob.
>
> You can ask for details e.g. on linux-arm-kernel at lists.infradead.org
> or try to search the Internet.
>
>> Right now I dont want to build dts as well as driver as a whole kernel
>> and building it as a loadable module.
>> Thanks in advance
>
>
>
> --
> Best regards,
> Jacek Anaszewski