Re: [PATCH v2 3/7] OvmfPkg: introduce PciCapPciIoLib

[Laszlo Ersek <lersek@redhat.com>]

On 05/24/18 10:13, Ard Biesheuvel wrote:
> On 23 May 2018 at 22:21, Laszlo Ersek <lersek@redhat.com> wrote:
>> Add a library class, and a UEFI_DRIVER lib instance, that are layered on
>> top of PciCapLib, and allow clients to plug an EFI_PCI_IO_PROTOCOL backend
>> into PciCapLib, for config space access.
>>
>> (Side note:
>>
> 
> Again, please retain the below.

Will do.

>> +STATIC
>> +EFI_STATUS
>> +ProtoDevTransferConfig (
>> +  IN     EFI_PCI_IO_PROTOCOL        *PciIo,
>> +  IN     EFI_PCI_IO_PROTOCOL_CONFIG TransferFunction,
>> +  IN     UINT16                     ConfigOffset,
>> +  IN OUT UINT8                      *Buffer,
>> +  IN     UINT16                     Size
>> +  )
>> +{
>> +  while (Size > 0) {
>> +    EFI_PCI_IO_PROTOCOL_WIDTH Width;
>> +    UINT16                    Count;
>> +    EFI_STATUS                Status;
>> +    UINT16                    Progress;
>> +
>> +    //
>> +    // Pick the largest access size that is allowed by the remaining transfer
>> +    // Size and by the alignment of ConfigOffset.
>> +    //
>> +    // When the largest access size is available, transfer as many bytes as
>> +    // possible in one iteration of the loop. Otherwise, transfer only one
>> +    // unit, to improve the alignment.
>> +    //
>> +    if (Size >= BIT2 && (ConfigOffset & (BIT2 - 1)) == 0) {
> 
> Ugh. Just use '4' or sizeof(UINT32).
> 
>> +      Width = EfiPciIoWidthUint32;
>> +      Count = Size >> Width;
>> +    } else if (Size >= BIT1 && (ConfigOffset & (BIT1 - 1)) == 0) {
>> +      Width = EfiPciIoWidthUint16;
>> +      Count = 1;
>> +    } else {
>> +      Width = EfiPciIoWidthUint8;
>> +      Count = 1;
>> +    }

I used "BITx" and "(BITx - 1)" for consistency, and because they seemed
to convey the idea well (namely, shifting down the alignment).

I'm fine replacing "BIT2" with "4", but then I believe I should also
replace "(BIT2 - 1)" with "3". Similarly, replace "BIT1" with "2", and
"(BIT1 -1)" with 1.

Do you prefer the current code or the decimal constants?

Thanks!
Laszlo