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Date: Thu, 13 Aug 2009 09:48:50 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] qdev: add return value to init() callbacks.
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To: Markus Armbruster <armbru@redhat.com>
Cc: Paul Brook <paul@codesourcery.com>, qemu-devel@nongnu.org

On 08/13/09 08:17, Markus Armbruster wrote:

> One problem with passing up error codes is diagnostics: when we reach
> the point where we can decide on policy, we've lost the context for
> precise diagnostics.  net.c tackles that problem by passing the
> destination for diagnostics down, to let code report errors with
> config_error() while remaining unaware of policy.

I don't want pass additional arguments all the way down just for error 
reporting.  One thing we can do is storing the error message in a global 
or thread-local variable (much like errno).  We could also add a errmsg 
field to DeviceState and use that.

> Issue also exists elsewhere.  Try monitor command "pci_add auto
> model=?".

Thats why I'd tend to use a global variable.  It also works in case 
don't have a DeviceState.

cheers,
   Gerd