Re: Closing PciIo protocol inside Stop()

[Arka Sharma <arka.sw1988@gmail.com>]

Actually I am thinking if it will be possible to use PciIo from a
driver on a ControllerHandle which managed by another driver which has
been stopped. So is it possible that driver which wants to access it
restarts the ControllerHandle with it's own DriverBindingHandle, or it
is that as soon as the driver closes PciIo and DevicePath on the
ControllerHandle inside Stop() function, the ControllerHandle is
destroyed.

On Thu, Dec 15, 2016 at 11:38 PM, Andrew Fish <afish@apple.com> wrote:
>
> On Dec 15, 2016, at 3:15 AM, Arka Sharma <arka.sw1988@gmail.com> wrote:
>
> I am wondering if the PciIo protocol instance for a PCI driver, is
> opened with _BY_DRIVER | EXCLUSIVE in Start() function, is not closed
> in the Stop() will the instance be uninstalled and the
> ControllerHandle removed ?
>
>
> Don't do that. The Start() and Stop() need to be symmetric. If you don't
> Stop() properly I think your Stop() function could get called again, and
> that would be really bad if you your driver was unloaded or something like
> that.
>
>
> Also is it possible to Close() the PciIo in Stop() and reopen the
> PciIo instance on the same controller handle from some other driver
> image with _BY_DRIVER attribute and accessing Pci resources on the
> ControllerHandle even after Stop() is called. I know it is not
> recommended way but curious about it. Or it could be specific to the
> implementation ?
>
>
> Maybe you should just ask what you want to do?
>
> If you just want to dump out PCI info you can use
> gEfiPciRootBridgeIoProtocolGuid ByProtocol. There is an example in the Shell
> PCI command:
> https://github.com/tianocore/edk2/blob/master/ShellPkg/Library/UefiShellDebug1CommandsLib/Pci.c#L2537
>
> Note: On a large server, or exotic SoC there could be multiple
> gEfiPciRootBridgeIoProtocolGuid instances, and the Shell command deals with
> that.
>
> Thanks,
>
> Andrew Fish
>
>
> Thanks & Regards,
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