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Subject: Re: [edk2-devel] [PATCH 1/1] ShellPkg: Do not connect handles without device paths
To: devel@edk2.groups.io, ray.ni@intel.com, vit9696 <vit9696@protonmail.com>,
 "Gao, Zhichao" <zhichao.gao@intel.com>
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From: "Laszlo Ersek" <lersek@redhat.com>
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Date: Mon, 13 Jan 2020 18:55:59 +0100
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On 01/13/20 12:56, Ni, Ray wrote:
> We shouldn't assume that a DriverBindingStart() can only start on a handle with device path installed. DevicePath protocol is just a special protocol.
> It's possible that a bus driver starts on a host controller handle and creates multiple children, each with only a Specific_IO protocol installed.
> Certain device driver can start on the children handle and open the Specific_IO protocol BY_DRIVER.
> I am not sure if certain today's network drivers may work like this. It's allowed per UEFI spec.

I agree.

Under "10.2 EFI Device Path Protocol", the spec says, "If the handle
does not logically map to a physical device, the handle may not
necessarily support the device path protocol."

I think gBS->ConnectController() and
EFI_DRIVER_BINDING_PROTOCOL.Supported() should work on such handles.

If we'd like to work around related issues in drivers, then I'd suggest
new command line options for the "load", "connect", "reconnect" shell
commands (maybe more), for filtering out handles that do not carry
device paths. Such command line options could be added as an extension,
IIUC, such as "-_option". I.e., I believe it's not necessary to start
with UEFI Shell Spec updates.

Thanks
Laszlo