Re: [Qemu-devel] [PATCHv2] parallel: Allow to disable CONFIG_PARALLEL

[Markus Armbruster <armbru@redhat.com>]

Miroslav Rezanina <mrezanin@redhat.com> writes:

> On Mon, May 11, 2015 at 08:46:19AM +0200, Markus Armbruster wrote:
>> mrezanin@redhat.com writes:
>> 
>> > From: Miroslav Rezanina <mrezanin@redhat.com>
>> >
>> > Disabling CONFIG_PARALLEL cause build failure as commit 07dc788 factored
>> > out initialization to parallel_hds_isa_init function in hw/char/parallel.c 
>> > that is not build. 
>> >
>> > Stub file is added to be able to disable CONFIG_PARALLEL. This file is used
>> > in targets using parallel_hds_isa_init and provide empty definition of this
>> > function.
>> >
>> > Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
>> >
>> > ---
>> >  hw/i386/Makefile.objs    | 1 +
>> >  hw/mips/Makefile.objs    | 2 ++
>> >  hw/sparc64/Makefile.objs | 2 ++
>> >  stubs/parallel-stub.c    | 7 +++++++
>> 
>> Nitpick: the existing stub/*.c naming practice suggests
>> stubs/parallel.c.
>
> Yeah...I forget to rename it after moving from repository
> root to stub directory. I originally have it in repository
> root as it is not included in libqemustub. So the naming can
> be treated as hint that something is different. However,
> I can rename it to follow stubs/* naming.
>> 
>> >  4 files changed, 12 insertions(+)
>> >  create mode 100644 stubs/parallel-stub.c
>> >
>> > diff --git a/hw/i386/Makefile.objs b/hw/i386/Makefile.objs
>> > index e058a39..2b7131a 100644
>> > --- a/hw/i386/Makefile.objs
>> > +++ b/hw/i386/Makefile.objs
>> > @@ -4,6 +4,7 @@ obj-y += pc.o pc_piix.o pc_q35.o
>> >  obj-y += pc_sysfw.o
>> >  obj-y += intel_iommu.o
>> >  obj-$(CONFIG_XEN) += ../xenpv/ xen/
>> > +obj-$(call lnot,$(CONFIG_PARALLEL)) += ../../stubs/parallel-stub.o
>> >  
>> >  obj-y += kvmvapic.o
>> >  obj-y += acpi-build.o
>> 
>> Can we rely on the linker to pull parallel-stub.o from a suitable .a
>> libqemustub.a when needed?
>
> We do not have to as parallel-stub.o is not included in libqemustub.a.
> It is linked directly in case CONFIG_PARALLEL is not defined (for
> targets using parallel_hds_isa_init).

No other stub is linked conditionally like that.  Instead we simply let
the linker pick up stubs as needed.  Let's do the same here.  Sketch:

diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
index 8beff4c..ad4e110 100644
--- a/stubs/Makefile.objs
+++ b/stubs/Makefile.objs
@@ -24,6 +24,7 @@ stub-obj-y += mon-printf.o
 stub-obj-y += mon-set-error.o
 stub-obj-y += monitor-init.o
 stub-obj-y += notify-event.o
+stub-obj-y += parallel.o
 stub-obj-$(CONFIG_SPICE) += qemu-chr-open-spice.o
 stub-obj-y += qtest.o
 stub-obj-y += reset.o
diff --git a/stubs/parallel.c b/stubs/parallel.c
new file mode 100644
index 0000000..2fa7e3a
--- /dev/null
+++ b/stubs/parallel.c
@@ -0,0 +1,12 @@
+#include "hw/i386/pc.h"
+
+void parallel_hds_isa_init(ISABus *bus, int n)
+{
+}
+
+bool parallel_mm_init(MemoryRegion *address_space,
+                      hwaddr base, int it_shift, qemu_irq irq,
+                      CharDriverState *chr)
+{
+    return false;
+}

Links fine with this crude test patch on top:

diff --git a/hw/char/Makefile.objs b/hw/char/Makefile.objs
index 5931cc8..c736436 100644
--- a/hw/char/Makefile.objs
+++ b/hw/char/Makefile.objs
@@ -1,6 +1,6 @@
 common-obj-$(CONFIG_IPACK) += ipoctal232.o
 common-obj-$(CONFIG_ESCC) += escc.o
-common-obj-$(CONFIG_PARALLEL) += parallel.o
+#common-obj-$(CONFIG_PARALLEL) += parallel.o
 common-obj-$(CONFIG_PL011) += pl011.o
 common-obj-$(CONFIG_SERIAL) += serial.o serial-isa.o
 common-obj-$(CONFIG_SERIAL_PCI) += serial-pci.o