Re: [Qemu-devel] [PATCH v3 8/8] hw/misc/edu: Compile the edu device as common object

[Paolo Bonzini]

----- Original Message -----
> From: "Thomas Huth" <address@hidden>
> To: "Richard Henderson" <address@hidden>, address@hidden, "Paolo Bonzini" 
> <address@hidden>
> Sent: Wednesday, June 21, 2017 3:40:31 AM
> Subject: Re: [PATCH v3 8/8] hw/misc/edu: Compile the edu device as common 
> object
> 
> On 20.06.2017 20:14, Richard Henderson wrote:
> > On 06/19/2017 10:52 PM, Thomas Huth wrote:
> >> edu.c does not contain any target-specific code, so we can put
> >> it into common-obj-y to compile it only once for all targets.
> >>
> >> Signed-off-by: Thomas Huth <address@hidden>
> > 
> > Isn't CONFIG_EDU defined by the target, via pci.conf?
> > Would it ever be set generically?
> 
> This is about Makefiles, not #defines in C sources ... so if I
> understand our build-system correctly, the variable is set for the
> Makefiles of the targets that use pci.mak. As far as I see, it gets
> compiled correctly here.
> And we've got plenty of those common-obj-$(CONFIG_xxx) statements
> elsewhere in this file (e.g. for CONFIG_PCI_TESTDEV which is also
> declared in default-configs/pci.mak), so this is just normal, no problem
> here, as far as I can tell.

Yes, the variable is evaluated once during the main directory build,
where it comes from config-all-devices.mak.  Then it is evaluated again
during the per-target build, where it comes from target-specific
configuration.

config-all-devices.mak should be documented in docs/devel/build-system.txt.

Paolo
Paolo