linux-kernel - Re: [PATCH] driver core: platform_bus: allow runtime override of dev_pm

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Date:	Mon, 23 Aug 2010 09:12:06 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Kevin Hilman <khilman@...prootsystems.com>,
	linux-kernel@...r.kernen.org
CC:	Magnus Damm <magnus.damm@...il.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, Paul Mundt <lethal@...ux-sh.org>,
	Magnus Damm <damm@...nsource.se>,
	Eric Miao <eric.y.miao@...il.com>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] driver core: platform_bus: allow runtime override of dev_pm_ops



"Kevin Hilman" <khilman@...prootsystems.com> wrote:

>From: Kevin Hilman <khilman@...com>
>
>Currently, the platform_bus allows customization of several of the
>busses dev_pm_ops methods by using weak symbols so that platform code
>can override them.  The weak-symbol approach is not scalable when
>wanting to support multiple platforms in a single kernel binary.
>
>Instead, provide __init methods for platform code to customize the
>dev_pm_ops methods at runtime.
>
>NOTE: after these dynamic methods are merged, the weak symbols should
>      be removed from drivers/base/platform.c.  AFAIK, this will only
>      affect SH and sh-mobile which should be converted to use this
>      runtime approach instead of the weak symbols.  After SH &
>      sh-mobile are converted, the weak symobols could be removed.
>
>Tested on OMAP3.
>
>Cc: Grant Likely <grant.likely@...retlab.ca>
>Cc: Magnus Damm <magnus.damm@...il.com>
>Signed-off-by: Kevin Hilman <khilman@...prootsystems.com>
>---
> drivers/base/platform.c         |   16 ++++++++++++++++
> include/linux/platform_device.h |    3 +++
> 2 files changed, 19 insertions(+), 0 deletions(-)
>
>diff --git a/drivers/base/platform.c b/drivers/base/platform.c
>index c6c933f..a7d8a00 100644
>--- a/drivers/base/platform.c
>+++ b/drivers/base/platform.c
>@@ -976,6 +976,22 @@ struct bus_type platform_bus_type = {
> };
> EXPORT_SYMBOL_GPL(platform_bus_type);
> 
>+const struct dev_pm_ops * __init platform_bus_get_pm_ops(void)
>+{
>+	struct bus_type *bus = &platform_bus_type;
>+
>+	return bus->pm;
>+}
>+
>+int __init platform_bus_set_pm_ops(struct dev_pm_ops *pm)
>+{
>+	struct bus_type *bus = &platform_bus_type;
>+
>+	bus->pm = pm;
>+
>+	return 0;
>+}
>+

Looks okay to me,  but these functions should have kerneldoc headers describing what they are, and more importantly, the constraints and what the acceptable use case is.

g.

> int __init platform_bus_init(void)
> {
> 	int error;
>diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
>index d7ecad0..4bce2c9 100644
>--- a/include/linux/platform_device.h
>+++ b/include/linux/platform_device.h
>@@ -138,6 +138,9 @@ extern struct platform_device *platform_create_bundle(struct platform_driver *dr
> 					struct resource *res, unsigned int n_res,
> 					const void *data, size_t size);
> 
>+extern const struct dev_pm_ops * __init platform_bus_get_pm_ops(void);
>+extern int __init platform_bus_set_pm_ops(struct dev_pm_ops *pm);
>+
> /* early platform driver interface */
> struct early_platform_driver {
> 	const char *class_str;
>-- 
>1.7.2.1
>

-- 
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