On Tue, Mar 22, 2005 at 09:02:24PM -0500, Jeff Garzik wrote:
> Kylene Hall wrote:
> >>what is the purpose of this pci_dev_get/put? attempting to prevent
> >>hotplug or
> >>something?
> >
> >
> >Seems that since there is a refernce to the device in the chip structure
> >and I am making the file private data pointer point to that chip structure
> >this is another reference that must be accounted for. If you remove it
> >with it open and attempt read or write bad things will happen. This isn't
> >really hotpluggable either as the TPM is on the motherboard.
>
> My point was that there will always be a reference -anyway-, AFAICS.
> There is a pci_dev reference assigned to the pci_driver when the PCI
> driver is loaded, and all uses by the TPM generic code of this pointer
> are -inside- the pci_driver's pci_dev object lifetime.
Think of the following situation:
- driver is bound to device.
- userspace opens char dev node.
- device is removed from the system (using fakephp I can do this
to _any_ pci device, even if it is on the motherboard.)
- userspace writes to char dev node
- driver attempts to access pci device structure that is no
longer present in memory.
Because of this open needs to get a reference to the pci device to
prevent oopses, or the driver needs to be aware of "device is now gone"
in some other manner.
thanks,
greg k-h
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