Re: UEFI_DRIVER dependencies

[Andrew Fish <afish@apple.com>]

> On May 17, 2017, at 10:00 PM, Kinney, Michael D <michael.d.kinney@intel.com> wrote:
> 
> Michael,
> 
> The UEFI Driver Model and the Driver Binding Protocol
> provide support for this case.  The idea is that a driver
> is loaded and started, but when a UEFI Driver is started,
> it only registers a Driver Binding Protocol.  Then in the 
> BDS phase, the devices required to boot are started using
> the UEFI Boot Service ConnectController() and
> ConnectController() calls the Driver Binding Protocol(s).
> 
> The dependencies between UEFI Drivers are in their Driver 
> Binding Protocols which are not used until after all of 
> the UEFI Drivers are loaded and started.
> 

Micheal,

1st off no dependency is really a dependency on all the architecture protocols, which is a fancy way of saying all the EFI Boot and Runtime Services are available. 

Lets say you have a driver that depends on DiskIo. The DiskIo driver depends on BlockIo. Now what happens when a disk driver is connected and produces a BlockIO is the DiskIo driver can know get connected. The DXE Core knows a protocol was added to the handle so it will keep trying to connect drivers to that handle as long as new protocols get added. So this is how the DriverBinding Support() is used to resolve the sequence issues. 

Thanks,

Andrew Fish

> Mike
> 
>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Michael
>> Zimmermann
>> Sent: Wednesday, May 17, 2017 9:43 PM
>> To: edk2-devel-01 <edk2-devel@lists.01.org>; Zeng, Star <star.zeng@intel.com>; Dong,
>> Eric <eric.dong@intel.com>
>> Subject: [edk2] UEFI_DRIVER dependencies
>> 
>> I know that UEFI_DRIVERs don't need or support Depex sections, but
>> what if an UEFI_DRIVER depends on a protocol provided by another
>> UEFI_DRIVER?
>> Since they get loaded automatically because I put them in my
>> platform's fdf, it raises the question of the loading order.
>> 
>> Will they get loaded in the order they're defined? How often will the
>> core retry if one of the drivers returns EFI_NOT_READY?
>> 
>> Thanks,
>> Michael
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