Re: Device count (to be done with)

[Stamatis Mitrofanis <ewstam@softhome.net>]

Oliver Neukum wrote:

>>The reason for all this fuss is that the hotplug scripts be able to
>>properly _un_load modules as well as loading them. Just consider what
>>happens when you have two USB HID mice and you unplug one of them. The
>>driver gets unloaded while it shouldn't (the other mouse is still in).
>>
>>I just noted that a very simple way to do this is to add a new
>>"should-count" in the module loading/unloading mechanism and extend
>>modprobe a bit to support it. That ought to be a very simple change.
>>Also, it is not really necessary for the kernel modules themselves to
>>support playing with this count (but it would be a good thing though).
>>
>>I hope I'm not missing anything. Please give me more details.
>>
>There should be indeed a second counter.
>However you would not want it in the module load and unload path. To make 
>sense it has to be incremented on device detection and decremented on device 
>removal. All you need now is to make it queryable from user space to let 
>modprobe check.
>For USB you increment on successful probe() and decrement on disconnect()
>
Apparently, we have two very similar proposals... :-)

If I got your idea right, you suggest that:
- should-count is stored for each kernel module, independent of 
"subsystem" (usb, pci etc.).
- when should-count is decremented to 0, the module is "autoclean".
- should-count is queried by kernel.
- should-count is incremented/decremented by kernel.
- should-count is queried by modprobe.

I was suggesting the following:
- should-count is stored for each kernel module, independent of "subsystem".
- when should-count is decremented to 0, the module is "autoclean".
- should-count is queried by kernel.
- should-count is incremented/decremented by kernel.
- should-count is queried by modprobe.
- should-count is incremented/decremented by modprobe.

It's just whether user-space is allowed to increment/decrement the count 
that differs. I believe that there has to be a user-space interface to 
this count since the should-count is abstract (hence not specific to 
PCI, USB or anything) and counts just "reasons for this module to remain 
loaded (not to be autocleaned)" . Thus, user-space may have its own set 
of reasons to have this module loaded in the kernel.

I think we've pretty much settled this issue. So now, the question is 
(again), who's going to write it...


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