[PATCH] alpha: Define pgprot_modify to silence tautological comparison warnings

Alpha's pgprot_noncached, pgprot_writecombine, and pgprot_device are
all identity macros, so the generic pgprot_modify() produces
tautological self-comparisons that GCC warns about:

  include/linux/pgtable.h:1701:25: warning: self-comparison always
  evaluates to true [-Wtautological-compare]

Since all caching attributes are no-ops on Alpha, define
pgprot_modify() to simply return newprot.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <[email protected]>
---
 arch/alpha/include/asm/pgtable.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git ./arch/alpha/include/asm/pgtable.h ./arch/alpha/include/asm/pgtable.h
index e786f630de5c..849abe2a1f98 100644
--- ./arch/alpha/include/asm/pgtable.h
+++ ./arch/alpha/include/asm/pgtable.h
@@ -126,6 +126,17 @@ struct vm_area_struct;
  */
 #define pgprot_noncached(prot)	(prot)
 
+/*
+ * All caching attribute macros are identity on Alpha, so the generic
+ * pgprot_modify() degenerates to tautological self-comparisons.
+ * Override it to just return newprot directly.
+ */
+#define pgprot_modify pgprot_modify
+static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
+{
+	return newprot;
+}
+
 /*
  * ZERO_PAGE is a global shared page that is always zero:  used
  * for zero-mapped memory areas etc..
-- 
2.52.0