Re: MdeModulePkg/SerialDxe: Inconsistent timeout processing in SerialRead

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

Hi Star,

I think your proposed patch is fine.

Thanks.

Gary (Heyi Guo)


在 7/18/2017 4:39 PM, Zeng, Star 写道:
> Gary,
> SerialDxe is a wrapper of SerialPortLib to produce serial io protocol.
> If let SerialDxe to handle the TimeOut, seemingly it can only check SerialPortPoll() and read data by SerialPortRead() one byte by one byte, for example like below.
> Do you have any proposed patch?
>
> Ray and Laszlo,
> Do you have any comments?
>
>
> ====================
> debf0d1b85e7a30defd29838abb20a44dd9ec69b
>   MdeModulePkg/Universal/SerialDxe/SerialIo.c | 18 ++++++++++++++++--
>   1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/MdeModulePkg/Universal/SerialDxe/SerialIo.c b/MdeModulePkg/Universal/SerialDxe/SerialIo.c
> index d2383e56dd8f..b05603d7f3b5 100644
> --- a/MdeModulePkg/Universal/SerialDxe/SerialIo.c
> +++ b/MdeModulePkg/Universal/SerialDxe/SerialIo.c
> @@ -465,11 +465,25 @@ SerialRead (
>     )
>   {
>     UINTN Count;
> +  UINTN TimeOut;
>   
>     Count = 0;
>   
> -  if (SerialPortPoll ()) {
> -    Count = SerialPortRead (Buffer, *BufferSize);
> +  while (Count < *BufferSize) {
> +    TimeOut = 0;
> +    while (TimeOut < mSerialIoMode.TimeOut) {
> +      if (SerialPortPoll ()) {
> +        break;
> +      }
> +      gBS->Stall (10);
> +      TimeOut += 10;
> +    }
> +    if (TimeOut >= mSerialIoMode.TimeOut) {
> +      break;
> +    }
> +    SerialPortRead (Buffer, 1);
> +    Count++;
> +    Buffer = (VOID *) ((UINT8 *) Buffer + 1);
>     }
>   
>     if (Count != *BufferSize) {
> ====================
>
>
> Thanks,
> Star
> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Heyi Guo
> Sent: Monday, July 17, 2017 12:23 PM
> To: edk2-devel@lists.01.org
> Subject: [edk2] MdeModulePkg/SerialDxe: Inconsistent timeout processing in SerialRead
>
> 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;
> }
>
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel