Optimization: keeping pointer all the time, or defining getter?

Rafał Miłecki zajec5 at gmail.com
Wed May 11 12:22:13 EDT 2011

I try to abstract bus in b43 driver. For frequently used fields
solution is obvious:
At init time I get info from bus-specific stuct and put it in generic field.
Example: core revision. We often refer to it, I put it in abstraction struct.

My question: what is the policy for cases with less frequently used fields?
Example: I need to use "struct device" for registering some low lever stuff.

I have two solutions:

1) Realtime:
struct device *get_device(...)
if (dev->bus_type = B43_BUS_SSB)
return dev->ssbdev->device;
else if (dev->bus_type = B43_BUS_BCMA)
return dev->bcmadev->device;

2) Init time:
void b43_ssb_init(struct ssb_device *ssbdev)
dev->struct = ssbdev->device;

The first one is slower but we don't keep "struct device" pointer in
abstraction struct. Situation is opposite for the second one.

Does anyone care? ;)


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