[Qemu-devel] ARM MCU Target Structure Question

[Carl Allendorph]

Hello All,

I'm working on a new microcontroller target (Atmel ATSAM4E) for the
qemu-system-arm executable. I've successfully setup a machine and created
some peripherals. I have some questions about how to structure the files
for contributing this target to the qemu project.

​In the current "hw" directory, there seems to be a mashup of MCU/board
machines, peripherals for these machines, and devices that would
communicate with these peripherals like I2C or SPI slave devices. There are
also general definitions for buses like I2C and SPI. There seem to be
peripherals for certain machines spread over several different directories.

For example, the omap*.c files are defined in the "arm" sub directory, and
then several of the peripherals are defined in the ssi/i2c/gpio/etc
directories. This seems inefficient from a development perspective because
the omap i2c/ssi/gpio peripherals are unlikely to be reused by other MCUs
or targets (except by derivatives in the OMAP family perhaps).

My preferred way to contribute to the project would be to create a new set
of directories in "hw/arm" that would have the following hierarchy:

  hw/arm/atmel/
    - utils/
    - atsam4/
      - common/    <-- Common Peripherals in family
      - atsam4e/   <-- Machine and Peripheral Definitions
      - atsam4n/
        ...
    - atsam3/        <-- Other families in the future?

Similarly, I would create an "include" structure for headers:

  include/hw/arm/atmel/
    - utils/
    - atsam4/
      - common/
      - atsam4e/
      - atsam4n/
        ...
    - atsam3/


Is this reasonable and acceptable?

I think refactoring the code in "hw" directory to organize machine targets
using similar logic for SOCs and moving slave device targets into a
separate subdirectory would be useful. I'm new to this project so perhaps
I'm missing something. I hope this does not come across as stepping on
anyones toes; that was not my intent.

Thanks in advanced for any comments or advice.