Re: [PATCH] ArmVirtPkg: use protocol-based DevicePathLib instance for most DXE modules

[Laszlo Ersek <lersek@redhat.com>]

On 04/24/18 08:16, Ard Biesheuvel wrote:
> On 24 April 2018 at 02:50, Laszlo Ersek <lersek@redhat.com> wrote:
>> Port OvmfPkg commit 5c3481b0b611e to ArmVirtPkg. Some explanation should
>> be in order (because 5c3481b0b611e doesn't offer any):
>>
>> - The UefiDevicePathLibDevicePathProtocol instance uses the Device Path
>>   Utilities Protocol, produced by DevicePathDxe, for formatting and
>>   parsing the textual device path representation. This allows for a
>>   lighter weight lib instance that gets linked into several DXE modules.
>>   In comparison, the more standalone UefiDevicePathLib instance includes
>>   the formatting and parsing routines in every client module.
>>
>> - The DXE core needs DevicePathLib before it dispatches DevicePathDxe, so
>>   it needs to stick with the standalone instance.
>>
>> - DevicePathDxe itself also needs the standalone instance, for
>>   implementing the protocol.
>>
>> - The DXE-phase PCD driver, "MdeModulePkg/Universal/PCD/Dxe/Pcd.inf",
>>   depends on DevicePathLib via UefiLib and DxeServicesLib at the least; so
>>   with this update, it inherits a dependency on the protocol. In reverse,
>>   DevicePathDxe depends on the PCD Protocol, via PcdLib. The cycle is
>>   broken by using BasePcdLibNull in DevicePathDxe. That restricts it to
>>   FixedAtBuild, Patch, and FeatureFlag PCDs, but that's fine.
>>
>> Example space savings (using ArmVirtQemu and the GCC5 toolchain):
>> - NOOPT:   187KB in FVMAIN, 12KB in FVMAIN_COMPACT
>> - DEBUG:   147KB in FVMAIN, 20KB in FVMAIN_COMPACT
>> - RELEASE: 123KB in FVMAIN, 17KB in FVMAIN_COMPACT
>>
>> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> Cc: Julien Grall <julien.grall@linaro.org>
>> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=940
>> Contributed-under: TianoCore Contribution Agreement 1.1
>> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> 
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Commit f9dff9028950.

Thanks!
Laszlo