[RFC PATCH V2 1/2] dtc: add 'compat' output option, prints board string

[Jason Cooper]

Consumers of the Linux kernel's build products are beginning to hardcode
the filenames of the dtbs generated.  Since the dtb filenames are
currently the dts filename s/dts/dtb/, this prevents the kernel
community from renaming dts files as needed.

Let's provide a consistent naming structure for consumers to script
against.  Or at least, as consistent as the dts properties themselves.

With this patch, adding the '-O compat' option to the dtc commandline
will cause dtc to parse the provided file, and print out the board
compatible string to stdout.

This will facilitate an 'installdtbs.sh' script in the kernel for naming
dtb files by their compatible string, eg:

$ dtc -I dtb -O compat arch/arm/boot/dts/armada-370-mirabox.dtb
globalscale,mirabox

This change will also simplify distribution install scripts that need to
search through many dtbs to find the right one for a target board.

Signed-off-by: Jason Cooper <jason at lakedaemon.net>
---
changes since v1:
 - made patch against in-tree dtc code to facilitate testing
 - dtc prints compatible string to stdout now, instead of creating symlink
    - should be more flexible for end-users

 scripts/dtc/dtc.c      | 3 +++
 scripts/dtc/dtc.h      | 1 +
 scripts/dtc/flattree.c | 9 +++++++++
 3 files changed, 13 insertions(+)

diff --git a/scripts/dtc/dtc.c b/scripts/dtc/dtc.c
index a375683c1534..89264bb0a3dd 100644
--- a/scripts/dtc/dtc.c
+++ b/scripts/dtc/dtc.c
@@ -68,6 +68,7 @@ static void  __attribute__ ((noreturn)) usage(void)
 	fprintf(stderr, "\t\tOutput formats are:\n");
 	fprintf(stderr, "\t\t\tdts - device tree source text\n");
 	fprintf(stderr, "\t\t\tdtb - device tree blob\n");
+	fprintf(stderr, "\t\t\tcompat - print board compatible string\n");
 	fprintf(stderr, "\t\t\tasm - assembler source\n");
 	fprintf(stderr, "\t-V <output version>\n");
 	fprintf(stderr, "\t\tBlob version to produce, defaults to %d (relevant for dtb\n\t\tand asm output only)\n", DEFAULT_FDT_VERSION);
@@ -250,6 +251,8 @@ int main(int argc, char *argv[])
 		dt_to_blob(outf, bi, outversion);
 	} else if (streq(outform, "asm")) {
 		dt_to_asm(outf, bi, outversion);
+	} else if (streq(outform, "compat")) {
+		dt_to_compat(bi);
 	} else if (streq(outform, "null")) {
 		/* do nothing */
 	} else {
diff --git a/scripts/dtc/dtc.h b/scripts/dtc/dtc.h
index 3e42a071070e..d4e47c697c2f 100644
--- a/scripts/dtc/dtc.h
+++ b/scripts/dtc/dtc.h
@@ -255,6 +255,7 @@ void process_checks(int force, struct boot_info *bi);
 
 void dt_to_blob(FILE *f, struct boot_info *bi, int version);
 void dt_to_asm(FILE *f, struct boot_info *bi, int version);
+void dt_to_compat(struct boot_info *bi);
 
 struct boot_info *dt_from_blob(const char *fname);
 
diff --git a/scripts/dtc/flattree.c b/scripts/dtc/flattree.c
index 665dad7bb465..bdbd3d7e8964 100644
--- a/scripts/dtc/flattree.c
+++ b/scripts/dtc/flattree.c
@@ -577,6 +577,15 @@ void dt_to_asm(FILE *f, struct boot_info *bi, int version)
 	data_free(strbuf);
 }
 
+void dt_to_compat(struct boot_info *bi)
+{
+	struct property *prop;
+
+	prop = get_property(bi->dt, "compatible");
+
+	printf("%s\n", prop->val.val);
+}
+
 struct inbuf {
 	char *base, *limit, *ptr;
 };
-- 
1.8.4.3