feature: support stm32f4 gpio output function and example app: gpioer

[benwei]

Here is first version of gpio function support , just gpio with output-only api.
An Example of gpioer with user the stm32f407 built-in four leds.
The gpioer app will make the 4 leds blink with 1 second interval.

[georgekang]

Because F9 is microkernel based, it would be better to put hardware driver in user space.
In my opinion, both user-log and user-gpioer violate the design principle of microkernel.
They will let F9 look like a monolithic kernel. user-log is a workaround just for easy dump but
not a good design.

[benwei]

Thank for your opinion. Sure, I agreed with you. Now, I'm trying to do the following modification.

firstly, I created all api related for gpio.c to gpioer.c (each function with __USER_TEXT).
let user/apps/gpioer/main.c call gpioer.c from user space.

secondly, the memory access fault because gpioer.c api access the following address

RCC_AHB1ENR,
GPIO_MODER(port);
GPIO_OTYPER(port)
GPIO_OSPEEDR(port)
GPIO_PUPDR(port)
GPIO_MODER(port)
GPIO_AFRL(port)
GPIO_AFRH(port)
GPIO_ODR(port)
Do you have any suggestion about memory permission ?
Should I grant all of the memory address to allow userspace gpioer app read/wrte? if doing by this way, how about the security control?

[benwei]

update gpioer sample code which access AHB1_1DEV from user space directly. because RCC_AHB1ENR(0x40023830) will be accessed, memory.c was modified with AHB1_1DEV's upbound range from 0x40022400 to 0x40023c00.

[benwei]

Thank for info. I referred the student code. That's great way to avoid hacking root_thread.c, I fixed code and remove duplicated code and put gpio.c to user mode. I extended the Kconfig for Applications to make default build original apps.

[jserv]

@benwei, please rebase to master.

In addition, @georgekang is going to revise the interrupt handling, and my student is working on the new driver model. We expect to make it fairly functioned next week.

[jserv]

WIP: user_interrupt branch

[jserv]

Cc. @slpbaby , who is working on STM32F429 Discovery platform support.
Cc. @rampant1018 , who is expected to revise further design of programming model and corresponding APIs.

[jserv]

Deprecated since we should always follow principle of least privilege (POLA).

[ab1aw]

I am trying to build an F9 image that can flash the LEDs on the STM32F407 Discovery board. I find that the forked repository of benwei does not build. I merged the benwei gpio code into my fork of latest f9-kernel. It builds successfully but does not run. Is there any successful code demonstration of flashing the LEDs? Thank you.