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

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Message-ID: <76e79aea-684a-4447-beb8-2d6a736b0950@email.android.com>
Date:	Mon, 23 Aug 2010 09:30:00 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Grant Likely <grant.likely@...retlab.ca>,
	Kevin Hilman <khilman@...prootsystems.com>
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



"Grant Likely" <grant.likely@...retlab.ca> wrote:

>
>
>"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;
>>+}
>>+

Another (minor) note, these can be more concise.  The set open function can have a void return, and bus = &platform_bus_type lines are unnecessary.

g.

>-- 
>Sent from my Android phone with K-9 Mail. Please excuse my brevity.

-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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