On Tue, Jun 30, 2009 at 5:03 PM, Robert P. J. Day <rpjday@xxxxxxxxxxxxxx> wrote:
>
> long story short, i was perusing the kernel source tree, looking for
> a random loadable module file to demonstrate the concept of a module
> init() routine undoing whatever work it had done in case it runs into
> an error, and i chanced across drivers/usb/gadget/dummy_hcd.c, where i
> saw at the bottom of the file:
>
> ... snip ...
>
> return retval;
>
> err_add_udc:
> platform_device_del(the_hcd_pdev);
> err_add_hcd:
> platform_driver_unregister(&dummy_udc_driver);
> err_register_udc_driver:
> platform_driver_unregister(&dummy_hcd_driver);
> err_register_hcd_driver:
> platform_device_put(the_udc_pdev);
> err_alloc_udc:
> platform_device_put(the_hcd_pdev);
> return retval;
> }
> module_init (init);
>
> static void __exit cleanup (void)
> {
> platform_device_unregister(the_udc_pdev);
> platform_device_unregister(the_hcd_pdev);
> platform_driver_unregister(&dummy_udc_driver);
> platform_driver_unregister(&dummy_hcd_driver);
> }
>
> note how the init() routine backs off on "the_udc_pdev" and
> "the_hcd_pdev" objects by calling platform_device_put(), while the
> exit() routine uses platform_device_unregister() instead. maybe i
> just don't understand enough about what's going on underneath. is
> there a reason that those two invocations don't match?
platform_device_unregister is just a wrapper for put and del so the
functionality remains the same! In case of init() it is error handling
so free whatever allocated.
>
> rday
> --
>
> ========================================================================
> Robert P. J. Day Waterloo, Ontario, CANADA
>
> Linux Consulting, Training and Annoying Kernel Pedantry.
>
> Web page: http://crashcourse.ca
> Linked In: http://www.linkedin.com/in/rpjday
> Twitter: http://twitter.com/rpjday
> ========================================================================
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