Re: [Qemu-devel] [PATCH V13 6/7] Introduce --enable-tpm-passthrough configure option

[Paul Brook <paul@codesourcery.com>]

> On 12/12/2011 11:51 PM, Paul Brook wrote:
> >>>> +tpm_passthrough="no"
> >>> 
> >>> Same as before, please probe for existence.
> >> 
> >> We would be probing for /dev/tpm0. Is that really what we want that this
> >> driver only gets compiled if /dev/tpm0 is (currently) available?
> > 
> > If what you say is true then this code should always be enabled.
> 
> Michael Tsirkin previously requested that there be an option for the TPM
> passthrough driver to be selectively enabled since at least using
> /dev/tpm0 may not be what everybody wants. The passthrough driver at
> some point will also be able to use sockets to communicate with a TPM
> when a file descriptor is passed to Qemu, so maybe that changes then?

Surely that's a runtime decision made by the qemu user, not a compile time 
decision made by the distribution vendor.  Testing functionality of the build 
machine is fundamentally wrong.  At best it completely breaks cross compiling, 
at worst it subtly breaks building on a dev machine and running on a 
production server.

Configure time probing only makes sense for code that will fail to build if 
external compile time dependencies are not present.

If you really think building qemu without this functionality is useful, then 
maybe add a configure option to disable it.  With the possible exception of 
developer debugging aids, code that is not enabled by default is clearly not 
worth having and should be removed altogether.

Paul