Re: [edk2-devel] [PATCH v1 1/1] ArmVirtPkg: Enable Early Serial For DxeCore

["Laszlo Ersek" <lersek@redhat.com>]

On 9/8/23 01:58, Sean Brogan wrote:
> 
> On 9/7/2023 1:54 PM, Laszlo Ersek wrote:
>> On 9/7/23 19:50, Sean Brogan wrote:
>>> I would argue that by declaring that your library class supports type
>>> DXE_CORE (or any core type) that you have declared you understand the
>>> uniqueness of the environment and have accounted for it.
>>>
>>> For instances that support DXE_CORE or MM_CORE module types we often use
>>> a global variable (to the library) to determine if the init routine has
>>> been completed.  This does require a single byte check on each serial
>>> message write (hot path) but given all the code on that path this is not
>>> noticeable in performance measurements.   In the case below this pattern
>>> could be used by the FdtPL011SerialPortLib to detect if it's init
>>> routine has been called.
>> Good point, but then I still claim that the "init check in each API"
>> should be done in a dedicated "DxeCoreDebugLibSerialPort" instance, and
>> not in a SerialPortLib instance. Here's why:
>>
>> (1) The SerialPortLib *class* requires SerialPortInitialize() to be
>> called before the other APIs.
> 
> Where do you see this? Looking at the file here:
> edk2/MdePkg/Include/Library/SerialPortLib.h at master · tianocore/edk2
> (github.com)
> <https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Library/SerialPortLib.h> I don't see that.  I don't necessarily disagree with you but I am just trying to find out where this is documented. 

I consider this an implicit requirement, from the first two sentences
(and from the fact that the function is declared at the top of the
header) -- "Initialize the serial device hardware. If no initialization
is required, then return RETURN_SUCCESS."

Laszlo



-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#108475): https://edk2.groups.io/g/devel/message/108475
Mute This Topic: https://groups.io/mt/101203427/7686176
Group Owner: devel+owner@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/leave/12367111/7686176/1913456212/xyzzy [rebecca@openfw.io]
-=-=-=-=-=-=-=-=-=-=-=-