On Wed, Sep 08, 2010 at 11:45:16AM -0700, Alison Chaiken wrote: > Josh Cartwright <joshc@xxxxxxxxx> wrote: > > __devinitdata is a preprocessor macro that will place the storage of the > > supported device PCI ID table in a specific section for special > > treatment. > > Thanks, that's *precisely* what I wanted to know. I will print your > answer out and stick it in the textbook. I see that the example is > confusing because it's essentially a reference to the kernel ABI, not > the API. Glad I could help. > As a general rule, I infer that when C looks peculiar and I can't > figure out what's going on from include/linux/*.h, I should consider l > looking at GCC docs instead. Its easy when you are new to the kernel to be overwhelmed by the boilerplate. I feel for you :). > This related question > > http://lkml.indiana.edu/hypermail/linux/kernel/0912.0/02339.html > > is interesting although it looks like no one answered. Well, I'm not sure exactly how these particular mechanisms work, but I can describe their intent, and I'll leave the understanding-the-implementation part as an exercise for you :). The __devinit and __devinitdata attributes put device initialization code and data in special sections which enable the kernel to make some memory-usage optimizations by controlling the lifetime of these sections in memory. If a kernel is built with hotplugging disabled, then all device initialization can be done one time, during boot, at which point the kernel can free up memory by freeing those pages holding the device initializing code and data. Like you were seeing before, when the kernel supports hotplugging (CONFIG_HOTPLUG is defined), then the kernel can't make the optimizing assumption that device initialization only happens at boot time, so nothing is gained by placing device initializing code and data into separate sections. I'm sure I missed some details, but the kernel source is all there to fill in the gaps :) -- -joshc -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
