Re: [Qemu-devel] [RFC] QOM design - add instance data to Object

[Peter Crosthwaite]

On Sat, Jun 13, 2015 at 11:57 AM, Liviu Ionescu <address@hidden> wrote:
>
>> On 13 Jun 2015, at 21:29, Peter Crosthwaite <address@hidden> wrote:
>>
>>
>> ... As all the information
>> you need to construct the object is constant per-concrete class, the
>> information can be added to the class to resolve.
>
> the one-instance-per-class might be true for MCUs, but generally it isn't, 
> for example the LED object, you can have several LEDs in a machine, all 
> having a common class, but different instances. similarly for GPIOs.
>

But there doesn't seem to be any demand for construction-sensitive
info there - at least yet.

> so, no, the class structure is not suitable for multi-instances objects, and 
> even for singletons I think that using it for passing such configuration data 
> is generally abusive.
>
>>> static STM32Capabilities stm32f103rb_capabilities = {
>>>    .cortexm = {
>>>        .device_name = TYPE_STM32F103RB,
>>
>> Why is the capabilities struct aware of its container type?
>
> ah, just for having the information available for verbosity. here is a 
> typical run for a simple blinky application:
>

can you use object_get_typename?

Regards,
Peter

> GNU ARM Eclipse 64-bits QEMU v2.3.50 (qemu-system-gnuarmeclipse).
> Board: 'STM32-H103' (Olimex Header Board for STM32F103RBT6 (Experimental)).
> Device: 'STM32F103RB' (Cortex-M3, MPU), Flash: 128 KB, RAM: 20 KB.
> Image: '/Users/ilg/My Files/MacBookPro Projects/GNU ARM Eclipse/Eclipse 
> Workspaces/qemu-images-44-osx/f1-h103-blink-sh-shd/Debug/f1-h103-blink-sh-shd.elf'.
> Command line: 'cm3 4' (5 bytes).
> Cortex-M3 core initialised.
> Cortex-M core reset.
>
> main(argc=2, argv=["cm3", "4"]);
> Hello ARM World!
> Standard output message.
> Standard error message.
> System clock: 72000000 Hz.
> [Green LED Off]
> [Green LED On]
> [Green LED Off]
> Second 1
> [Green LED On]
> [Green LED Off]
> Second 2
> [Green LED On]
> [Green LED Off]
> Second 3
> [Green LED On]
> [Green LED Off]
> Second 4
> QEMU exit(0)
>
>> Why do you need to make it one giant struct with its own inheritance
>> hierarchy? With the class idea, you would just split this to two
>> structs for cortexm and stm32.
>
> sure, this can be done, but when using constructors, this requires passing 
> two pointers instead of one.
>
>
> regards,
>
> Liviu
>
>
>
>