sandbox: Add a -T flag to use the test device tree

U-Boot already supports using -D to indicate that it should use the normal
device tree. It is sometimes useful to run with the test device tree, e.g.
when running a test. Add a -T option for this along with some
documentation.

It can be used like this:

   /tmp/b/sandbox/u-boot -T -c "ut dm pci_busdev"

(this will use /tmp/b/sandbox/arch/sandbox/dts/test.dtb as the DT)
Signed-off-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>
Tested-by: NBin Meng <bmeng.cn@gmail.com>

arch/sandbox/cpu/start.c

@@ -147,6 +147,31 @@ static int sandbox_cmdline_cb_default_fdt(struct sandbox_state *state,
 SANDBOX_CMDLINE_OPT_SHORT(default_fdt, 'D', 0,
 		"Use the default u-boot.dtb control FDT in U-Boot directory");
 
+static int sandbox_cmdline_cb_test_fdt(struct sandbox_state *state,
+				       const char *arg)
+{
+	const char *fmt = "/arch/sandbox/dts/test.dtb";
+	char *p;
+	char *fname;
+	int len;
+
+	len = strlen(state->argv[0]) + strlen(fmt) + 1;
+	fname = os_malloc(len);
+	if (!fname)
+		return -ENOMEM;
+	strcpy(fname, state->argv[0]);
+	p = strrchr(fname, '/');
+	if (!p)
+		p = fname + strlen(fname);
+	len -= p - fname;
+	snprintf(p, len, fmt, p);
+	state->fdt_fname = fname;
+
+	return 0;
+}
+SANDBOX_CMDLINE_OPT_SHORT(test_fdt, 'T', 0,
+			  "Use the test.dtb control FDT in U-Boot directory");
+
 static int sandbox_cmdline_cb_interactive(struct sandbox_state *state,
 					  const char *arg)
 {

doc/arch/sandbox.rst

@@ -103,6 +103,8 @@ A device tree binary file can be provided with -d. If you edit the source
 (it is stored at arch/sandbox/dts/sandbox.dts) you must rebuild U-Boot to
 recreate the binary file.
 
+To use the default device tree, use -D. To use the test device tree, use -T.
+
 To execute commands directly, use the -c option. You can specify a single
 command, or multiple commands separated by a semicolon, as is normal in
 U-Boot. Be careful with quoting as the shell will normally process and
@@ -499,6 +501,13 @@ run natively on your board if desired (and enabled).
 
 To run all tests use "make check".
 
+To run a single test in an existing sandbox build, you can use -T to use the
+test device tree, and -c to select the test:
+
+  /tmp/b/sandbox/u-boot -T -c "ut dm pci_busdev"
+
+This runs dm_test_pci_busdev() which is in test/dm/pci.c
+
 
 Memory Map
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