Re: [PATCH v2 1/3] drivers/bus: Add Legacy PM OPS usage check andwarning to bus_register()

From: Shuah Khan
Date: Mon Jan 06 2014 - 15:30:41 EST

On 01/06/2014 01:17 PM, Greg KH wrote:
On Mon, Jan 06, 2014 at 01:03:21PM -0700, Shuah Khan wrote:
Add Legacy PM OPS usage checks to bus_register() function. If Legacy PM OPS
usage is found, print warning message to indicate that the driver code needs
updating to use Dev PM OPS interfaces. This will help serve as a way to track
drivers that still use Legacy PM OPS and fix them.

The Legacy PM OPS check looks for suspend(struct device *, pm_message_t) or
resume(struct device *) bus level interfaces.

Signed-off-by: Shuah Khan <>
drivers/base/bus.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 73f6c29..e8753a7 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -916,6 +916,9 @@ int bus_register(struct bus_type *bus)
goto bus_groups_fail;

pr_debug("bus: '%s': registered\n", bus->name);
+ if (bus->suspend || bus->resume)
+ pr_warn("bus '%s' needs updating - use pm pointer.\n",
+ bus->name);

Why can't we just sweep the tree for all of these now, fix them up, and
then delete these fields and be done with it?

Same for the other ones, putting warnings in the kernel log files
doesn't work at all for getting people to fix up their code (see
examples of scsi log messages being there for _years_ about obsolete
driver interfaces being used.)

This change is not a simple case of replacing legacy with pm ops. I have been working on changing drivers that use legacy, in some cases it is an easy change, however in some cases it requires adding new interfaces to port over from legacy to pm ops. Legacy suspend/resume is more course grain and pm ops offer fine grain control over suspend, hibernate etc. Also it has been a challenge without the hardware to test.

My thinking is adding warning might get the attention of individual driver owners.

-- Shuah

Shuah Khan
Senior Linux Kernel Developer - Open Source Group
Samsung Research America(Silicon Valley) | (970) 672-0658
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