Re: [Qemu-devel] [PATCH 7/9] qdev: Use QError for not found error

[Anthony Liguori <aliguori@us.ibm.com>]

Daniel P. Berrange wrote:
> hink just returning error codes to the client is far too little
> information. I don't think we need the fully normalized structure
> that Luiz originally proposed with bus/dev addresses split out, but
> we certainly need to include a string description giving as much
> detail as possible.  If attaching a host USB device failed, I don't
> want a single error code  QERR_OPEN_FAILED, nor a generic message 
> like 'could not open device', i want the exact details, eg
>
>   'could not open device: permission denied' 
>   'could not open device: no such file or directory' 
>   'could not open device: device or resource busy' 
>
> The localization issue is somewhat of a red herring though. This string
> description is not something that clients would ultimately expose to the
> user. The client apps would likely present a more generic error message
> to the user, based off the error code. The error description received
> from QEMU will instead be written out to the logs as a record for later
> troubleshooting. eg if the user files a bug report, it will include the
> full error details, so libvirt/qemu maintainers have a better chance of
> figuring out what went wrong.
>   

But then advanced users end up doing silly things like analyzing libvirt 
logs.  Why do that when your own example is obviously "could not open 
device: %s", strerror(errno).   We should pass {"error" : {"type": 
"OpenFailedException", "errno": errno}}

-- 
Regards,

Anthony Liguori