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Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for
From: |
Alexander Graf |
Subject: |
Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding |
Date: |
Wed, 10 Sep 2014 16:38:40 +0200 |
> Am 10.09.2014 um 16:18 schrieb Paolo Bonzini <address@hidden>:
>
> Il 10/09/2014 15:51, Eric Auger ha scritto:
>>> On 09/10/2014 12:09 PM, Alexander Graf wrote:
>>>
>>>
>>>> On 10.09.14 12:05, Paolo Bonzini wrote:
>>>> Il 10/09/2014 11:56, Alexander Graf ha scritto:
>>>>>
>>>>>
>>>>>> On 10.09.14 11:43, Paolo Bonzini wrote:
>>>>>> Il 10/09/2014 11:31, Alexander Graf ha scritto:
>>>>>>>>> Yeah, please do the registration in sysbus.c, not in virt.c. There is
>>>>>>>>> no reason to make the platform_bus_init_notify+DynSysbusNotifier
>>>>>>>>> interface public. The code in sysbus.c can fill in the fields.
>>>>>>> Sysbus != Platform bus. Sysbus is an in-QEMU representation of a
>>>>>>> pseudo-bus that we put all devices onto that we consider unsorted.
>>>>>>>
>>>>>>> Platform bus is a machine representation of an actual bus that devices
>>>>>>> are attached to. These devices usually are sysbus devices.
>>>>>>
>>>>>> Is there any difference between the two?
>>>>>>
>>>>>> Take a machine that has two chips, a SoC that does everything except
>>>>>> USB, and a USB controller chip.
>>>>>>
>>>>>> Strictly speaking the USB controller chip would be on a "platform bus",
>>>>>> but we would likely put it on sysbus.
>>>>>>
>>>>>> Why should it matter whether the devices are static or dynamic, for the
>>>>>> sake of calling something the "system" or the "platform" bus? I would
>>>>>> say that QEMU calls "sysbus" the platform bus.
>>>>>>
>>>>>> Some devices (e.g. the local APIC in x86, or the in-core timers and GIC
>>>>>> in ARM) should probably not be in sysbus at all, and should attach
>>>>>> directly to the CPU address space. But that is a quirk in the modeling
>>>>>> of those devices, it shouldn't mean that sysbus is not a "platform" bus.
>>>>>
>>>>> On e500 for example, we have a predefined CCSR region. That is a machine
>>>>> defined "platform bus". The offsets inside that region are strictly
>>>>> defined by the spec.
>>>>>
>>>>> Now take the serial ports. We have space for 2 serial ports inside of
>>>>> that CCSR region. We can spawn these 2 ports in the machine file based
>>>>> on -serial, but if you want to spawn them with -device, how do you tell
>>>>> the machine whether they should go into the "big bucket platform bus" or
>>>>> the "CCSR platform bus"?
>>>>
>>>> Two possibilities:
>>>>
>>>> 1) you would use two instances of sysbus (one default, one created by
>>>> the board) and specify ",bus=ccsr" on the command line when you want to
>>>> add the device to the CCSR region.
>>>>
>>>> The two would work exactly the same way, only with different algorithms
>>>> for resource allocation.
>>>>
>>>> 2) similar to ISA, you would create a new ccsr-bus device and a new
>>>> ccsr-serial device, and use -device ccsr-serial,index=[0|1],chardev=foo
>>>> to specify which of the two serial ports this is for. Most of the fdt
>>>> magic could be shared by the sysbus and CCSR cases.
>>>>
>>>> I think I prefer (2)...
>>>
>>> Fair enough.
>>>
>>> As far as moving "platform bus" logic into sysbus, I'd really like to
>>> hold back and see what this whole thing ends up getting used for first.
>>>
>>> So for now, I'd definitely prefer to keep "platform bus" logic and
>>> "sysbus" logic separate. If we realize that every user only ever uses
>>> the dynamic sysbus creation in conjunction with our "platform bus"
>>> implementation, we can merge them.
>>
>> Hi Paolo, Alex,
>>
>> I understand I keep the code in a separate module from sysbus.c. Is that
>> the shared conclusion?
>
> I don't think so, but maybe I misunderstood what Alex wrote.
I still think it shouldn't be inside the sysbus files. You can use sysbus
devices without a platform bus.
Alex
>
> Paolo
>
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, (continued)
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Alexander Graf, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Paolo Bonzini, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Alexander Graf, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Paolo Bonzini, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Alexander Graf, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Paolo Bonzini, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Alexander Graf, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Paolo Bonzini, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Eric Auger, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Paolo Bonzini, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding,
Alexander Graf <=
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Paolo Bonzini, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Alexander Graf, 2014/09/10
- Re: [Qemu-devel] [PATCH v3 1/6] hw/misc/dyn_sysbus_binding: helpers for sysbus device dynamic binding, Paolo Bonzini, 2014/09/10
[Qemu-devel] [PATCH v3 2/6] hw/arm/dyn_sysbus_devtree: helpers for sysbus device dynamic dt node generation, Eric Auger, 2014/09/09