Re: [PATCH 2/2] gpio: sch: Add interrupt support
From: Jan Kiszka
Date: Fri Apr 26 2019 - 13:40:19 EST
On 26.04.19 19:33, Manivannan Sadhasivam wrote:
On Fri, Apr 26, 2019 at 08:20:19PM +0300, Andy Shevchenko wrote:
On Fri, Apr 26, 2019 at 7:05 PM Jan Kiszka <jan.kiszka@xxxxxxxxxxx> wrote:
On 26.04.19 16:42, Enrico Weigelt, metux IT consult wrote:
On 26.04.19 15:36, Jan Kiszka wrote:
At the same time, there are no real alternatives - to my> knowledge - for the value it brings (various bindings) to simply
switch> the engine.
Which value exactly does that collection of crude wrappers and broken
attempts to buypass the kernel (driving gpios via /dev/mem *facepalm*)
provide ?
Leaving that blunt hack aside:
import mraa
pin = mraa.Gpio(13)
pin.dir(mraa.DIR_OUT)
pin.write(1)
And the same goes for nodejs, java and c++.
Moreover, this allows you to abstract away where "Pin 13" actually came from on
that board if the kernel changes (BSP -> upstream...) or the extension board or
...
The problem here is opaque number. This has to be chip + *relative* pin number/
See this:
https://stackoverflow.com/questions/55532410/how-do-linux-gpio-numbers-get-their-values/55579640#55579640
But for platform like 96Boards we don't need controller specific lookup, these
are all handled by the platform code [1] so that the users can use the standard
pinout number to access GPIOs. For instance, pin 23 on the Low Speed expansion
header is the GPIO for all 96Boards platform, so the user can access that pin
using 23 itself in the application and it will run across all supported
96Boards.
Can you ensure stable numbering when probing order changes, e.g. due to adding
an extension board?
Jan
That's one of the reason why we prefer MRAA.
Thanks,
Mani
[1] https://github.com/intel-iot-devkit/mraa/blob/master/src/arm/96boards.c#L75
--
With Best Regards,
Andy Shevchenko
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux