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Subject[PATCH 11/12] misc: implement a dummy early platform driver
Date
From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Implement a very simple early platform driver. Its purpose is to show
how such drivers can be registered and to emit a message when probed.

It can be then added to the device tree or machine code to verify that
the early platform devices work as expected.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/misc/Kconfig | 8 ++++
drivers/misc/Makefile | 1 +
drivers/misc/dummy-early.c | 82 ++++++++++++++++++++++++++++++++++++++
3 files changed, 91 insertions(+)
create mode 100644 drivers/misc/dummy-early.c

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 5d713008749b..60fef04eb236 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -91,6 +91,14 @@ config DUMMY_IRQ
The sole purpose of this module is to help with debugging of systems on
which spurious IRQs would happen on disabled IRQ vector.

+config DUMMY_EARLY
+ bool "Dummy early platform driver"
+ select EARLY_PLATFORM
+ default n
+ help
+ This module's only function is to register itself with the early
+ platform device framework and be probed early in the boot process.
+
config IBM_ASM
tristate "Device driver for IBM RSA service processor"
depends on X86 && PCI && INPUT
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index d0a8788d5151..6170855853a1 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_INTEL_MID_PTI) += pti.o
obj-$(CONFIG_ATMEL_SSC) += atmel-ssc.o
obj-$(CONFIG_ATMEL_TCLIB) += atmel_tclib.o
obj-$(CONFIG_DUMMY_IRQ) += dummy-irq.o
+obj-$(CONFIG_DUMMY_EARLY) += dummy-early.o
obj-$(CONFIG_ICS932S401) += ics932s401.o
obj-$(CONFIG_LKDTM) += lkdtm/
obj-$(CONFIG_TIFM_CORE) += tifm_core.o
diff --git a/drivers/misc/dummy-early.c b/drivers/misc/dummy-early.c
new file mode 100644
index 000000000000..eb8f826aea64
--- /dev/null
+++ b/drivers/misc/dummy-early.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Texas Instruments
+ *
+ * Author:
+ * Bartosz Golaszewski <bgolaszewski@baylibre.com>
+ *
+ * Dummy testing driver whose only purpose is to be registered and probed
+ * using the early platform device mechanism.
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/early_platform.h>
+
+struct dummy_early_data {
+ int a;
+ int b;
+};
+
+static int dummy_early_probe_early(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct dummy_early_data *data;
+ struct resource *res;
+
+ dev_notice(dev, "dummy-early driver probed early!\n");
+
+ data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ data->a = 123;
+ data->b = 321;
+
+ dev_dbg(dev, "setting driver data early: a = %d, b = %d\n",
+ data->a, data->b);
+ dev_set_drvdata(dev, data);
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (res)
+ dev_dbg(dev, "got early resource: start = 0x%08x, end = 0x%08x\n",
+ res->start, res->end);
+
+ return 0;
+}
+
+static int dummy_early_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct dummy_early_data *data;
+
+ dev_notice(dev, "dummy-early driver probed late!\n");
+ data = dev_get_drvdata(dev);
+ dev_dbg(dev, "retrieving driver data late: a = %d, b = %d\n",
+ data->a, data->b);
+
+ return 0;
+}
+
+static const struct of_device_id dummy_early_of_match[] = {
+ { .compatible = "dummy-early", },
+ { },
+};
+
+static struct early_platform_driver dummy_early_driver = {
+ .early_probe = dummy_early_probe_early,
+ .pdrv = {
+ .probe = dummy_early_probe,
+ .driver = {
+ .name = "dummy-early",
+ .of_match_table = dummy_early_of_match,
+ },
+ }
+};
+module_early_platform_driver(dummy_early_driver);
+
+MODULE_AUTHOR("Bartosz Golaszewski <bgolaszewski@baylibre.com>");
+MODULE_DESCRIPTION("Dummy early platform device driver");
+MODULE_LICENSE("GPL v2");
--
2.17.0
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