Re: MdeModulePkg/SerialDxe: Inconsistent timeout processing in SerialRead

[Heyi Guo <heyi.guo@linaro.org>]

+cc maintainers :)


在 7/17/2017 12:23 PM, Heyi Guo 写道:
> Hi Folks,
>
> In SerialRead function in MdeModulePkg/Universal/SerialDxe/SerialIo.c, 
> it seems the timeout processing in SerialRead is not consistent.
>
> Since SerialPortPoll only checks the status of serial port and returns 
> immediately, and SerialPortRead does not really implement a time out 
> mechanism and will always wait for enough input, it will cause below 
> results:
>
> 1. If there is no serial input at all, this interface will return 
> timeout immediately without any waiting;
>
> 2. If there is A characters in serial port FIFO, and caller requires 
> A+1 characters, it will wait until a new input is coming and timeout 
> will not really occur.
>
> As SerialPortLib is a simple library implementation, I think it is 
> better to improve SerialIoDxe driver instead of SerialPortLib.
>
> Please let me know your comments about this.
>
> Thanks and regards,
>
> Gary (Heyi Guo)
>
> EFI_STATUS
> EFIAPI
> SerialRead (
>   IN EFI_SERIAL_IO_PROTOCOL *This,
>   IN OUT UINTN              *BufferSize,
>   OUT VOID                  *Buffer
>   )
> {
>   UINTN Count;
>
>   Count = 0;
>
>   if (SerialPortPoll ()) {
>     Count = SerialPortRead (Buffer, *BufferSize);
>   }
>
>   if (Count != *BufferSize) {
>     *BufferSize = Count;
>     return EFI_TIMEOUT;
>   }
>
>   return EFI_SUCCESS;
> }
>