Re: [Qemu-devel] '.' IDs and certain names breaks -global and -set

[Markus Armbruster]

Alistair Francis <address@hidden> writes:

> On Wed, Apr 9, 2014 at 9:58 PM, Peter Crosthwaite
> <address@hidden> wrote:
>> On Wed, Apr 9, 2014 at 7:56 PM, Markus Armbruster <address@hidden> wrote:
>>> We have a number of device model names containing '.'.  They're unusable
>>> with -global.  That's because "-global A.B.C=foo" gets parsed as
>>>
>>>     driver = "A"
>>>     property = "B.C"
>>>     value = "foo".
>>>
>>> Wrong when the device model name is really A.B and the property is C,
>>> e.g. "-global cfi.pflash01.name".
>>>
>>> Related problem: QemuOpts ID may contain '.'.  Such IDs are in fact
>>> common practice.  Unfortunately, they're unusable with -set.  For
>>> instance, -set A.B.C.D=foo gets parsed as
>>>
>>>     group = "A"
>>>     id = "B"
>>>     arg = "C.D"
>>>     value = "foo"
>>>
>>> Wrong when the id is really B.C and the arg is D, e.g. "-device
>>> isa-serial,id=s.0 -set device.s.0.chardev=c0".  This issue isn't limited
>>> to devices.
>>>
>>> Related historical problem: commit b560a9a.
>>>
>>> Possible solutions:
>>>
>>> * Outlaw '.' in QemuOpts parameter names (and thus device model names
>>>   and property names, because QemuOpts is a major way for users to
>>>   specify them).
>>>
>>
>> I like the "."s because they mean "this is where the vendor stops and
>> the IP name starts". Whereas "-" just delimits multiple words. We seem
>> to be running our of characters however with these overloading
>> problems. But AFAICT ":" is largely unused (within this context
>> anyway). So how about:
>>
>> "-" seperates multiple words in a name
>> ":" splits logical groupings of multiple words as appropriate ( e.g.
>> some-vendor:their-device )
>> "," demilits multiple command line arguments
>> "." accesses property within an object
>> "/" walks the canonical path
>>
>> I do also need to confess to my alternate agenda of device tree driven
>> QEMU - I am still parsing device trees and directly mapping the
>> compatible strings to QOM type names for machine creation. Ambiguity
>> of "-" as meaning the "," or the "-" is hard to deal with.
>>
>> Regards,
>> Peter
>>
>>> * Resolve the syntactic ambiguity semantically (ugh)
>>>
>>> * Extend the syntax of -global and -set to let users avoid the issue, or
>>>   replace them outright
>>>
>>> * Use the old ostrich algorithm
>>>
>>> Andreas, what restrictions does QOM place on QOM path component names?
>>> No '/', obviously.  Anything else?
>>>
>>
>
> What is the consensus with this? I like Peter's naming suggestions as
> they are straight
> forward and don't break any compatibility.

I'd like to hear a few more opinions, Andreas's in particular.  Give him
a bit more time to chime in.