gpio-led driver

[Jacek Anaszewski]

On 07/22/2016 12:10 PM, Raul Piper wrote:
> On Thu, Jul 21, 2016 at 12:10 PM, Jacek Anaszewski
> <j.anaszewski at 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