[PATCH 3/4] add rtas_service_present() helper

[Nathan Lynch]

To test for the existence of an RTAS function, we typically do:

   foo_token = rtas_token("foo");
   if (foo_token == RTAS_UNKNOWN_SERVICE)
      return;

Add a rtas_service_present method, which provides a more conventional
boolean interface for testing the existence of an RTAS method.

Signed-off-by: Nathan Lynch <ntl at pobox.com>
---
 arch/powerpc/kernel/rtas.c |    6 ++++++
 include/asm-powerpc/rtas.h |    1 +
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 387ed0d..7970bed 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -303,6 +303,12 @@ int rtas_token(const char *service)
 }
 EXPORT_SYMBOL(rtas_token);
 
+int rtas_service_present(const char *service)
+{
+	return rtas_token(service) != RTAS_UNKNOWN_SERVICE;
+}
+EXPORT_SYMBOL(rtas_service_present);
+
 #ifdef CONFIG_RTAS_ERROR_LOGGING
 /*
  * Return the firmware-specified size of the error log buffer
diff --git a/include/asm-powerpc/rtas.h b/include/asm-powerpc/rtas.h
index 5a0c136..f08f356 100644
--- a/include/asm-powerpc/rtas.h
+++ b/include/asm-powerpc/rtas.h
@@ -159,6 +159,7 @@ extern struct rtas_t rtas;
 
 extern void enter_rtas(unsigned long);
 extern int rtas_token(const char *service);
+extern int rtas_service_present(const char *service);
 extern int rtas_call(int token, int, int, int *, ...);
 extern void rtas_restart(char *cmd);
 extern void rtas_power_off(void);
-- 
1.4.4.1