dm: Add a No-op uclass

This uclass is intended for devices that do not need any features from the
uclass, including binding children.
This will typically be used by devices that are used to bind child devices
but do not use dm_scan_fdt_dev() to do it. That is for example the case of
several USB wrappers that have 2 child devices (1 for device and 1 for
host) but bind only one at a any given time.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

5 files changed, 92 insertions, 0 deletions

diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 8b2d6451c6..c328258901 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -400,6 +400,18 @@
 		sandbox,silent;	/* Don't emit sounds while testing */
 	};
 
+	nop-test_0 {
+		compatible = "sandbox,nop_sandbox1";
+		nop-test_1 {
+			compatible = "sandbox,nop_sandbox2";
+			bind = "True";
+		};
+		nop-test_2 {
+			compatible = "sandbox,nop_sandbox2";
+			bind = "False";
+		};
+	};
+
 	misc-test {
 		compatible = "sandbox,misc_sandbox";
 	};
diff --git a/drivers/core/uclass.c b/drivers/core/uclass.c
index fc3157de39..dc9eb62893 100644
--- a/drivers/core/uclass.c
+++ b/drivers/core/uclass.c
@@ -757,3 +757,8 @@ int uclass_pre_remove_device(struct udevice *dev)
 	return 0;
 }
 #endif
+
+UCLASS_DRIVER(nop) = {
+	.id		= UCLASS_NOP,
+	.name		= "nop",
+};
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index 09e0ad5391..418392875c 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -62,6 +62,7 @@ enum uclass_id {
 	UCLASS_MMC,		/* SD / MMC card or chip */
 	UCLASS_MOD_EXP,		/* RSA Mod Exp device */
 	UCLASS_MTD,		/* Memory Technology Device (MTD) device */
+	UCLASS_NOP,		/* No-op devices */
 	UCLASS_NORTHBRIDGE,	/* Intel Northbridge / SDRAM controller */
 	UCLASS_NVME,		/* NVM Express device */
 	UCLASS_PANEL,		/* Display panel, such as an LCD */
diff --git a/test/dm/Makefile b/test/dm/Makefile
index 49857c5092..aeb3aa0ca7 100644
--- a/test/dm/Makefile
+++ b/test/dm/Makefile
@@ -3,6 +3,7 @@
 # Copyright (c) 2013 Google, Inc
 
 obj-$(CONFIG_UT_DM) += bus.o
+obj-$(CONFIG_UT_DM) += nop.o
 obj-$(CONFIG_UT_DM) += test-driver.o
 obj-$(CONFIG_UT_DM) += test-fdt.o
 obj-$(CONFIG_UT_DM) += test-main.o
diff --git a/test/dm/nop.c b/test/dm/nop.c
new file mode 100644
index 0000000000..2df29f3d15
--- /dev/null
+++ b/test/dm/nop.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Test for the NOP uclass
+ *
+ * (C) Copyright 2019 - Texas Instruments Incorporated - http://www.ti.com/
+ * Jean-Jacques Hiblot <jjhiblot@ti.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <dm/ofnode.h>
+#include <dm/lists.h>
+#include <dm/device.h>
+#include <dm/test.h>
+#include <misc.h>
+#include <test/ut.h>
+
+static int noptest_bind(struct udevice *parent)
+{
+	ofnode ofnode = dev_read_first_subnode(parent);
+
+	while (ofnode_valid(ofnode)) {
+		struct udevice *dev;
+		const char *bind_flag = ofnode_read_string(ofnode, "bind");
+
+		if (bind_flag && (strcmp(bind_flag, "True") == 0))
+			lists_bind_fdt(parent, ofnode, &dev, false);
+		ofnode = dev_read_next_subnode(ofnode);
+	}
+
+	return 0;
+}
+
+static const struct udevice_id noptest1_ids[] = {
+	{
+		.compatible = "sandbox,nop_sandbox1",
+	},
+	{ }
+};
+
+U_BOOT_DRIVER(noptest_drv1) = {
+	.name	= "noptest1_drv",
+	.of_match	= noptest1_ids,
+	.id	= UCLASS_NOP,
+	.bind = noptest_bind,
+};
+
+static const struct udevice_id noptest2_ids[] = {
+	{
+		.compatible = "sandbox,nop_sandbox2",
+	},
+	{ }
+};
+
+U_BOOT_DRIVER(noptest_drv2) = {
+	.name	= "noptest2_drv",
+	.of_match	= noptest2_ids,
+	.id	= UCLASS_NOP,
+};
+
+static int dm_test_nop(struct unit_test_state *uts)
+{
+	struct udevice *dev;
+
+	ut_assertok(uclass_get_device_by_name(UCLASS_NOP, "nop-test_0", &dev));
+	ut_assertok(uclass_get_device_by_name(UCLASS_NOP, "nop-test_1", &dev));
+	ut_asserteq(-ENODEV,
+		    uclass_get_device_by_name(UCLASS_NOP, "nop-test_2", &dev));
+
+	return 0;
+}
+
+DM_TEST(dm_test_nop, DM_TESTF_FLAT_TREE | DM_TESTF_SCAN_FDT);