Driver Core: early platform driver

V3 of the early platform driver implementation.

Platform drivers are great for embedded platforms because we can separate
driver configuration from the actual driver.  So base addresses,
interrupts and other configuration can be kept with the processor or board
code, and the platform driver can be reused by many different platforms.

For early devices we have nothing today.  For instance, to configure early
timers and early serial ports we cannot use platform devices.  This
because the setup order during boot.  Timers are needed before the
platform driver core code is available.  The same goes for early printk
support.  Early in this case means before initcalls.

These early drivers today have their configuration either hard coded or
they receive it using some special configuration method.  This is working
quite well, but if we want to support both regular kernel modules and
early devices then we need to have two ways of configuring the same
driver.  A single way would be better.

The early platform driver patch is basically a set of functions that allow
drivers to register themselves and architecture code to locate them and
probe.  Registration happens through early_param().  The time for the
probe is decided by the architecture code.

See Documentation/driver-model/platform.txt for more details.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Magnus Damm <damm@igel.co.jp>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: David Brownell <david-b@pacbell.net>
Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 43 insertions, 0 deletions

diff --git a/include/linux/init.h b/include/linux/init.h
index 68cb0265d00..f121a7a10c3 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -247,6 +247,7 @@ struct obs_kernel_param {
 
 /* Relies on boot_command_line being set */
 void __init parse_early_param(void);
+void __init parse_early_options(char *cmdline);
 #endif /* __ASSEMBLY__ */
 
 /**
diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 76e470a299b..72736fd8223 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -77,4 +77,46 @@ extern int platform_driver_probe(struct platform_driver *driver,
 #define platform_get_drvdata(_dev)	dev_get_drvdata(&(_dev)->dev)
 #define platform_set_drvdata(_dev,data)	dev_set_drvdata(&(_dev)->dev, (data))
 
+/* early platform driver interface */
+struct early_platform_driver {
+	const char *class_str;
+	struct platform_driver *pdrv;
+	struct list_head list;
+	int requested_id;
+};
+
+#define EARLY_PLATFORM_ID_UNSET -2
+#define EARLY_PLATFORM_ID_ERROR -3
+
+extern int early_platform_driver_register(struct early_platform_driver *epdrv,
+					  char *buf);
+extern void early_platform_add_devices(struct platform_device **devs, int num);
+
+static inline int is_early_platform_device(struct platform_device *pdev)
+{
+	return !pdev->dev.driver;
+}
+
+extern void early_platform_driver_register_all(char *class_str);
+extern int early_platform_driver_probe(char *class_str,
+				       int nr_probe, int user_only);
+extern void early_platform_cleanup(void);
+
+
+#ifndef MODULE
+#define early_platform_init(class_string, platform_driver)		\
+static __initdata struct early_platform_driver early_driver = {		\
+	.class_str = class_string,					\
+	.pdrv = platform_driver,					\
+	.requested_id = EARLY_PLATFORM_ID_UNSET,			\
+};									\
+static int __init early_platform_driver_setup_func(char *buf)		\
+{									\
+	return early_platform_driver_register(&early_driver, buf);	\
+}									\
+early_param(class_string, early_platform_driver_setup_func)
+#else /* MODULE */
+#define early_platform_init(class_string, platform_driver)
+#endif /* MODULE */
+
 #endif /* _PLATFORM_DEVICE_H_ */