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Subject: Re: [edk2-devel] VirtIO Sound Driver (GSoC 2021)
To: Ethin Probst <harlydavidsen@gmail.com>, devel@edk2.groups.io
Cc: Andrew Fish <afish@apple.com>, Mike Kinney <michael.d.kinney@intel.com>,
 Leif Lindholm <leif@nuviainc.com>, Laszlo Ersek <lersek@redhat.com>,
 "Desimone, Nathaniel L" <nathaniel.l.desimone@intel.com>,
 Rafael Rodrigues Machado <rafaelrodrigues.machado@gmail.com>,
 Gerd Hoffmann <kraxel@redhat.com>
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From: "Michael Brown" <mcb30@ipxe.org>
Message-ID: <4f029f76-0f11-f229-af04-2407ac80308b@ipxe.org>
Date: Fri, 16 Apr 2021 02:03:56 +0100
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On 16/04/2021 01:59, Ethin Probst wrote:
> Also, I'm a bit confused. I've looked at several VirtIO devices now
> and have seen things like this:
> #define VIRTIO_PCI_DEVICE_SIGNATURE   SIGNATURE_32 ('V', 'P', 'C', 'I')
> // ...
>    UINT32                 Signature;
> I'm quite confused because I can't seem to find this anywhere in the
> VirtIO specification. The spec says nothing about signature values
> anywhere, just the magic value of 0x74726976. So where does this come
> from?

 From a quick look at the code, it seems to be a private signature value 
applied to a software-only data structure used by the UEFI driver, and 
is used solely for sanity checking that a pointer is pointing to the 
right kind of object.

Michael