[PATCH -next 3/4] spi: mockup: Add runtime device tree overlay interface

[Wei Yongjun <weiyongjun1@xxxxxxxxxx>]

Add a runtime device tree overlay interface for device need dts file.
With it its possible to use device tree overlays without having to use
a per-platform overlay manager.

Add a new device by command:
$ cat test.dtbo > /sys/class/spi_master/spi0/overlay_fdto

Remove the device by command:
$ echo remove > /sys/class/spi_master/spi0/overlay_fdto

Signed-off-by: Wei Yongjun <weiyongjun1@xxxxxxxxxx>
---
 drivers/spi/Kconfig      |  2 ++
 drivers/spi/spi-mockup.c | 48 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index e0f0fa2746ad..4b7c84ddb367 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -1161,6 +1161,8 @@ config SPI_TLE62X0
 config SPI_MOCKUP
 	tristate "SPI controller Testing Driver"
 	depends on OF
+	select OF_EARLY_FLATTREE
+	select OF_RESOLVE
 	select BPF_EVENTS
 	help
 	  This enables SPI controller testing driver, which provides a way to
diff --git a/drivers/spi/spi-mockup.c b/drivers/spi/spi-mockup.c
index 7a93b194ee53..404ad821bf6a 100644
--- a/drivers/spi/spi-mockup.c
+++ b/drivers/spi/spi-mockup.c
@@ -21,6 +21,9 @@
 struct mockup_spi {
 	struct mutex lock;
 	struct spi_device *devs[MOCKUP_CHIPSELECT_MAX];
+
+	void *fdto;
+	int ovcs_id;
 };
 
 static struct spi_master *to_spi_master(struct device *dev)
@@ -145,9 +148,53 @@ delete_device_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_WO(delete_device);
 
+static ssize_t
+overlay_fdto_store(struct device *dev, struct device_attribute *attr,
+		   const char *buf, size_t count)
+{
+	struct spi_master *master = to_spi_master(dev);
+	struct mockup_spi *mock = spi_master_get_devdata(master);
+	int ret;
+
+	mutex_lock(&mock->lock);
+
+	if (strncmp(buf, "remove\n", count) == 0) {
+		if (mock->ovcs_id < 0) {
+			ret = -ENOENT;
+			goto out_unlock;
+		}
+		of_overlay_remove(&mock->ovcs_id);
+		kfree(mock->fdto);
+		mock->ovcs_id = -1;
+		mock->fdto = NULL;
+	} else {
+		if (mock->ovcs_id >= 0) {
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+		mock->fdto = kmemdup(buf, count, GFP_KERNEL);
+		if (!mock->fdto) {
+			ret = -ENOMEM;
+			goto out_unlock;
+		}
+		ret = of_overlay_fdt_apply(mock->fdto, count, &mock->ovcs_id);
+		if (ret < 0)
+			goto out_unlock;
+	}
+
+	mutex_unlock(&mock->lock);
+	return count;
+
+out_unlock:
+	mutex_unlock(&mock->lock);
+	return ret;
+}
+static DEVICE_ATTR_WO(overlay_fdto);
+
 static struct attribute *spi_mockup_attrs[] = {
 	&dev_attr_new_device.attr,
 	&dev_attr_delete_device.attr,
+	&dev_attr_overlay_fdto.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(spi_mockup);
@@ -227,6 +274,7 @@ static int spi_mockup_probe(struct platform_device *pdev)
 
 	mock = spi_master_get_devdata(master);
 	mutex_init(&mock->lock);
+	mock->ovcs_id = -1;
 
 	ret = spi_register_master(master);
 	if (ret) {
-- 
2.34.1