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Re: [Qemu-devel] [PATCH v2 03/15] qdev: Allow device addressing via 'dri
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v2 03/15] qdev: Allow device addressing via 'driver.instance' |
Date: |
Mon, 31 May 2010 10:43:50 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
Jan Kiszka <address@hidden> writes:
> Markus Armbruster wrote:
>> Jan Kiszka <address@hidden> writes:
>>
>>> From: Jan Kiszka <address@hidden>
>>>
>>> Extend qbus_find_dev to allow addressing of devices without an unique id
>>> via an optional per-bus instance number. The new formats are
>>> 'driver.instance' and 'alias.instance'.
>>>
>>> Signed-off-by: Jan Kiszka <address@hidden>
>>> ---
>>> docs/qdev-device-use.txt | 12 +++++++++++-
>>> hw/qdev.c | 23 ++++++++++++++++++-----
>>> 2 files changed, 29 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/docs/qdev-device-use.txt b/docs/qdev-device-use.txt
>>> index 9ac1fa1..5939481 100644
>>> --- a/docs/qdev-device-use.txt
>>> +++ b/docs/qdev-device-use.txt
>>> @@ -1,6 +1,6 @@
>>> = How to convert to -device & friends =
>>>
>>> -=== Specifying Bus and Address on Bus ===
>>> +=== Specifying Bus, Address on Bus, and Devices ===
>>>
>>> In qdev, each device has a parent bus. Some devices provide one or
>>> more buses for children. You can specify a device's parent bus with
>>> @@ -24,6 +24,16 @@ Furthermore, if a device only hosts a single bus, the
>>> bus name can be
>>> omitted in the path. Example: /i440FX-pcihost/PIIX3 abbreviates
>>> /i440FX-pcihost/pci.0/PIIX3/isa.0 as none of the buses has siblings.
>>>
>>> +Existing devices can be addressed either via a unique ID if it was
>>> +assigned during creation or via the device tree path:
>>> +
>>> +/full_bus_address/driver_name[.instance_number]
>>> + or
>>> +abbreviated_bus_address/driver_name[.instance_number]
>>> +
>>> +Example: /i440FX-pcihost/pci.0/e1000.2 addresses the second e1000
>>> +adapter on the bus 'pci.0'.
>>> +
>>> Note: the USB device address can't be controlled at this time.
>>
>> "instance number" isn't defined in this document.
>
> True, only implicitly via the example.
>
>>
>> I understand the problem you're trying to solve; I've had it myself many
>> times. But is inventing an instance number the right solution?
>>
>> The two e1000 devices already have a perfectly fine unique identifier on
>> their bus: their bus address. What about recognizing bus addresses in
>> paths? Requires a suitable restriction on device names and IDs to avoid
>> ambiguity, say "start with letter".
>>
>> qdev currently doesn't abstract bus addresses, but that's fixable.
>
> You would also have to specify unique addressing scheme to those buses
> that do not have it yet. E.g. what should be the address of a ISA bus
> device? The base of its first ioport range? But if it does not have any
> as it only injects ISA IRQs?
Hmm, instance numbers are the lesser evil in this case.
Define them properly, and make info qtree show them, and we'll be okay,
I guess.
[Qemu-devel] [PATCH v2 04/15] qdev: Convert device and bus lists to QTAILQ, Jan Kiszka, 2010/05/22
[Qemu-devel] [PATCH v2 05/15] qdev: Allow device specification by qtree path for device_del, Jan Kiszka, 2010/05/22
[Qemu-devel] [PATCH v2 07/15] monitor: Add completion for qdev paths, Jan Kiszka, 2010/05/22
[Qemu-devel] [PATCH v2 11/15] monitor: return length of printed string via monitor_[v]printf, Jan Kiszka, 2010/05/22
[Qemu-devel] [PATCH v2 09/15] QMP: Reserve namespace for complex object classes, Jan Kiszka, 2010/05/22