On Thu, 23 Nov 2017, Greg Kroah-Hartman wrote:
On Thu, Nov 23, 2017 at 11:24:38AM +1100, Finn Thain wrote:
On Mon, 20 Nov 2017, I wrote:
You need to free up the memory allocated, and I don't see that
happening here ... The kernel should yell at you ...
WARN(1, KERN_ERR "Device '%s' does not have a release() "
"function, it is broken and must be fixed.\n",
dev_name(dev));
This won't fire unless device_del() is called, right?
Sorry, I should have written, "This won't fire unless
device_unregister() is called, right?" -- though I guess it could be
any call to put_device().
If need be I can add code to cleanly tear down the bus devices and the
associated linked lists and procfs structures, just prior to kernel
termination, as a kernel exitcall. But I don't see this pattern in
use.
When the kernel shuts down, no, the devices are not removed.
But what happens when the bus code is unloaded if it is built as a
module? The devices will be removed then. Or they should be.
This bus driver is not a module.
So please implement the remove device code path,
OK.
just because some other busses are buggy that way does not mean you need
to duplicate their incorrect behavior.
Actually, I think the bug is in porting.txt, when it says "Optionally, the
bus driver may set the device's name and release fields."
It's not clear to me that the extra complexity is worth it. This may
explain the other devices which never get unregistered (e.g.
rtc_device, rtc_efi_dev, etc.)
I've read Documentation/driver-model/ and watched your presentations
on this topic but it's unclear to me whether you are saying in this
thread that calling device_unregister() is mandatory.
It sounds like you are saying that a non-NULL device.release method is
mandatory (which is easily solved with an empty function). But
Documentation/driver-model/porting.txt says the release method is
optional.
If you provide a non-NULL empty release function, you get to be made fun
of, as per the in-kernel kobject documentation. The kernel is trying to
save you from yourself, that warning is not there just to try to work
around.
That warning never shows up at all, because it would only ever appear at
device_unregister() time, rather than at device_register() time.
Anyway, I will read the in-kernel comments in the kobject code. Thanks for
the tip.
--
thanks,
greg k-h
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