-all-files := $(header-y) $(objhdr-y) $(genhdr-y) $(wrapper-files)
-input-files := $(addprefix $(srctree)/$(obj)/,$(header-y)) \
- $(addprefix $(objtree)/$(obj)/,$(objhdr-y)) \
- $(addprefix $(objtree)/$(gen)/,$(genhdr-y))
-output-files := $(addprefix $(install)/, $(all-files))
+all-files := $(header-y) $(genhdr-y) $(wrapper-files)
+output-files := $(addprefix $(installdir)/, $(all-files))
+
+input-files := $(foreach hdr, $(header-y), \
+ $(or \
+ $(wildcard $(srcdir)/$(hdr)), \
+ $(wildcard $(oldsrcdir)/$(hdr)), \
+ $(error Missing UAPI file $(srcdir)/$(hdr)) \
+ )) \
+ $(foreach hdr, $(genhdr-y), \
+ $(or \
+ $(wildcard $(gendir)/$(hdr)), \
+ $(error Missing generated UAPI file $(gendir)/$(hdr)) \
+ ))