On Sun, Feb 21, 2016 at 03:10:30PM +0200, Michael S. Tsirkin wrote:

On Sun, Feb 21, 2016 at 08:06:17AM -0500, Gabriel L. Somlo wrote:

quoted

quoted

quoted

+#if !(defined(FW_CFG_CTRL_OFF) && defined(FW_CTRL_DATA_OFF))
+# if (defined(CONFIG_ARM) || defined(CONFIG_ARM64))
+#  define FW_CFG_CTRL_OFF 0x08
+#  define FW_CFG_DATA_OFF 0x00
+# elif (defined(CONFIG_PPC_PMAC) || defined(CONFIG_SPARC32)) /* ppc/mac,sun4m */
+#  define FW_CFG_CTRL_OFF 0x00
+#  define FW_CFG_DATA_OFF 0x02
+# elif (defined(CONFIG_X86) || defined(CONFIG_SPARC64)) /* x86, sun4u */
+#  define FW_CFG_CTRL_OFF 0x00
+#  define FW_CFG_DATA_OFF 0x01
+# else
+#  warning "QEMU FW_CFG may not be available on this architecture!"
+#  define FW_CFG_CTRL_OFF 0x00
+#  define FW_CFG_DATA_OFF 0x01

Better not try hacks like this, they are hard
to support down the road. Please only list what is tested and
actually exposed by QEMU.

I was looking for a standard way to advertise register offsets within
the ioport or mmio region assigned to fw_cfg, but right now the answer
is "there isn't one", and "register offsets are an arch specific
detail". As such, the only reasonable way I saw was to copy the same
values used in the QEMU source.

See also:
https://lists.gnu.org/archive/html/qemu-devel/2015-11/msg05037.html
 
Thanks much,
--Gabriel

My point is you don't know what will qemu do on these
other arches which do not at the moment have fw cfg.
So don't try to guess!

Oh, you mean for the "else". I originally wanted to be able to compile
this on any architecture and wanted some dummy defaults I could
override on the command line. But now we're already restricting this
to known architectures only, so I'll send a patch turning the warning
into an error, and removing the #defines for the "else" branch above.

Sorry I misunderstood you the first time around :)

Thanks,
--Gabriel