[PATCH 1/2] x86: add a user configurable Kconfig option for the NS16550 UART

[Derek Straka <derek@asterius.io>]

Allows for the conditional inclusion of NS16550 UART driver on the x86 platform
rather than having it always enabled.

The default configuration for the HAS_NS16550 option remains 'y' on x86, so the
behavior out of the box remains unchanged.  The addition of the option allows
advanced users to enable/disable the inclusion of the NS16550 UART driver.

Signed-off-by: Derek Straka <derek@asterius.io>
---
 xen/arch/x86/Kconfig     | 1 -
 xen/drivers/char/Kconfig | 4 ++--
 xen/include/xen/serial.h | 7 ++++++-
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 265fd79..8a122df 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -15,7 +15,6 @@ config X86
 	select HAS_MEM_ACCESS
 	select HAS_MEM_PAGING
 	select HAS_MEM_SHARING
-	select HAS_NS16550
 	select HAS_PASSTHROUGH
 	select HAS_PCI
 	select HAS_PDX
diff --git a/xen/drivers/char/Kconfig b/xen/drivers/char/Kconfig
index 51343d0..c87e018 100644
--- a/xen/drivers/char/Kconfig
+++ b/xen/drivers/char/Kconfig
@@ -1,6 +1,6 @@
 config HAS_NS16550
-	bool
-	default y
+	bool "NS16550 UART" if EXPERT = "y"
+	default y if X86
 	help
 	  This selects the 16550-series UART support. For most systems, say Y.
 
diff --git a/xen/include/xen/serial.h b/xen/include/xen/serial.h
index 1212a12..343779c 100644
--- a/xen/include/xen/serial.h
+++ b/xen/include/xen/serial.h
@@ -167,9 +167,14 @@ struct ns16550_defaults {
     int irq;       /* default irq */
     unsigned long io_base; /* default io_base address */
 };
+
+#ifdef CONFIG_HAS_NS16550
 void ns16550_init(int index, struct ns16550_defaults *defaults);
-void ehci_dbgp_init(void);
+#else
+static inline void ns16550_init(int index, struct ns16550_defaults *defaults) {}
+#endif
 
+void ehci_dbgp_init(void);
 void arm_uart_init(void);
 
 struct physdev_dbgp_op;
-- 
2.7.4


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