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DateSun, 10 Dec 2006 00:25:08 -0700
FromGrant Grundler <>
SubjectRe: [PATCH 1/5] Update Documentation/pci.txt
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On Tue, Dec 05, 2006 at 11:26:51PM -0800, Greg KH wrote: ...
I do have a few minor comments:
...
Please mark the initialization and cleanup functions where appropriate (the corresponding macros are defined in <linux/init.h>):
__init Initialization code. Thrown away after the driver initializes.
__exit Exit code. Ignored for non-modular drivers. __devinit Device initialization code. Identical to __init if the kernel is not compiled with CONFIG_HOTPLUG, normal function otherwise.
__devexit The same for __exit.

Tips on marks:
o The module_init()/module_exit() functions (and all initialization functions called _only_ from these) should be marked __init/__exit.
o The struct pci_driver shouldn't be marked with any of these tags.
o The ID table array should be marked __devinitdata.
o The probe() and remove() functions (and all initialization functions called only from these) should be marked __devinit and __devexit.

o If the driver is not a hotplug driver then use only __init/__exit and __initdata/__exitdata.

No, don't say this, pci drivers are not "hotplug drivers",

agreed - removed that bullet item.

and since CONFIG_HOTPLUG is really hard to turn off these days, don't confuse people with the devinit stuff. Everyone gets it wrong...

While revisiting this bit, I started thinking:

o While I agree HOTPLUG is essential to desktop and server, I don't think that's true for "embedded" (e.g. routers/switches).
o drivers should use __dev* exactly because HOTPLUG is defined.
o Why does everyone get __dev* wrong? Bad API? Missing or bad Documentation? [ This is not a free-for-all...I'd like a clear answer from Greg what would help driver writers get this right. ]
o Prefer a seperate patch to clean this up?
Take what I have for now and sort out the __devinit handling in another round?

o Note what I have is essentially the original text - just reformatted to be a bit more readable.

o Hrm...what did greg mean with "it"? All of the markers? Or just the __dev* markers?

o Pointers to functions marked as __devexit must be created using __devexit_p(function_name). That will generate the function name or NULL if the __devexit function will be discarded.

I really recommend just not using any of these for almost all PCI drivers, as the space savings just really isn't there...

It's a bit too late for that, no?
And even if it's more of a PITA than it's worth, we do save something:
# hppa64-linux-gnu-readelf -S vmlinux
...
 [26] .init.text        PROGBITS         0000000040598000  00457000
      0000000000022280  0000000000000000  AX       0     0     8
 [27] .init.data        PROGBITS         00000000405ba280  00479280
      000000000001faf0  0000000000000000  WA       0     0     8
...
Reality is they are used in _alot_ of drivers.
I checked 2.6.19:
grundler <514>find -name \*.c | xargs fgrep __devinit | wc
   2723   16812  235863
I'd prefer to keep the short references here if you don't mind too much. At least until you can get some consensus that __init and __exit should go away
or get replaced by easier-to-get-right markers.

thanks,
grant
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