Re: MdeModulePkg/SerialDxe: SetAttributes() not follow UEFI spec

["Zeng, Star" <star.zeng@intel.com>]

Yes, there may be slowing down perceived with 1s time out. https://github.com/tianocore/edk2/commit/a7fd8452964c1a6ffeee1fe07537cb900c0ccb07

But, my understanding to Heyi's question is that caller should be aware default time out value (1000000) will be used if the 0 time out value is input. That should follow UEFI spec and the implementation in MdeModulePkg/Bus/Pci/PciSioSerialDxe and IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe.


Thanks,
Star
-----Original Message-----
From: Laszlo Ersek [mailto:lersek@redhat.com] 
Sent: Friday, March 23, 2018 10:32 PM
To: Zeng, Star <star.zeng@intel.com>; Guo Heyi <heyi.guo@linaro.org>; edk2-devel@lists.01.org
Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>
Subject: Re: [edk2] MdeModulePkg/SerialDxe: SetAttributes() not follow UEFI spec

On 03/23/18 01:50, Zeng, Star wrote:
> I agree.

Wasn't there a problem with the default timeout being 1 second, and that
1 second slowing down terminal I/O on some platform? I don't remember more precisely.

Thanks
Laszlo

> -----Original Message-----
> From: Guo Heyi [mailto:heyi.guo@linaro.org]
> Sent: Thursday, March 22, 2018 7:43 PM
> To: edk2-devel@lists.01.org
> Cc: Zeng, Star <star.zeng@intel.com>; Dong, Eric 
> <eric.dong@intel.com>; Ni, Ruiyu <ruiyu.ni@intel.com>
> Subject: Re: MdeModulePkg/SerialDxe: SetAttributes() not follow UEFI 
> spec
> 
> +cc Maintainers of MdeModulePkg.
> 
> On Thu, Mar 22, 2018 at 07:39:42PM +0800, Guo Heyi wrote:
>> Hi folks,
>>
>> The SetAttributes() interface of generic SerialDxe driver in 
>> MdeModulePkg/Universal does not fully follow UEFI spec. The spec 
>> requires to use default time out value when the input "Timeout" is 0, 
>> but the current implementation will set timeout to 0 directly.  It 
>> tries to pass "Timeout" to SerialPortSetAttributes(), but none of 
>> SerialPortLib instances in edk2 tree will deal with this parameter.
>> What's more, Timeout is actually a software parameter and is only 
>> used in SerialDxe itself, not in SerialPortLib instances, so I think 
>> it makes more sense to set Timeout in SerialDxe directly instead of in SerialPortLib.
>>
>> Please advise.
>>
>> Thanks and regards,
>>
>> Heyi
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