Re: [PATCH v3 1/5] MdeModulePkg: introduce non-discoverable device protocol

["Ni, Ruiyu" <ruiyu.ni@intel.com>]

Regards,
Ray

>-----Original Message-----
>From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Ard Biesheuvel
>Sent: Friday, November 18, 2016 12:59 PM
>To: Ni, Ruiyu <ruiyu.ni@intel.com>
>Cc: Kinney, Michael D <michael.d.kinney@intel.com>; edk2-devel@lists.01.org; Gao, Liming <liming.gao@intel.com>;
>afish@apple.com; Leif Lindholm <leif.lindholm@linaro.org>
>Subject: Re: [edk2] [PATCH v3 1/5] MdeModulePkg: introduce non-discoverable device protocol
>
>On 18 November 2016 at 02:11, Ni, Ruiyu <ruiyu.ni@intel.com> wrote:
>>
>>
>> Regards,
>> Ray
>>
>>>-----Original Message-----
>>>From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
>>>Sent: Thursday, November 17, 2016 6:43 PM
>>>To: Ni, Ruiyu <ruiyu.ni@intel.com>
>>>Cc: Kinney, Michael D <michael.d.kinney@intel.com>; edk2-devel@lists.01.org; Gao, Liming <liming.gao@intel.com>;
>>>afish@apple.com; Leif Lindholm <leif.lindholm@linaro.org>
>>>Subject: Re: [edk2] [PATCH v3 1/5] MdeModulePkg: introduce non-discoverable device protocol
>>>
>>>
>>>> On 17 Nov 2016, at 08:52, Ni, Ruiyu <ruiyu.ni@intel.com> wrote:
>>>>
>>>>
>>>>
>>>> Thanks/Ray
>>>>
>>>>> -----Original Message-----
>>>>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
>>>>> Ard Biesheuvel
>>>>> Sent: Thursday, November 17, 2016 2:07 PM
>>>>> To: Ni, Ruiyu <ruiyu.ni@intel.com>
>>>>> Cc: Kinney, Michael D <michael.d.kinney@intel.com>; edk2-
>>>>> devel@lists.01.org; Gao, Liming <liming.gao@intel.com>; afish@apple.com;
>>>>> Leif Lindholm <leif.lindholm@linaro.org>
>>>>> Subject: Re: [edk2] [PATCH v3 1/5] MdeModulePkg: introduce non-
>>>>> discoverable device protocol
>>>>>
>>>>>
>>>>>
>>>>>> On 17 Nov 2016, at 02:53, Ni, Ruiyu <ruiyu.ni@intel.com> wrote:
>>>>>>
>>>>>> Ard,
>>>>>> I have two comments in below.
>>>>>>
>>>>>> Thanks/Ray
>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf
>>>>>>> Of Leif Lindholm
>>>>>>> Sent: Thursday, November 17, 2016 1:49 AM
>>>>>>> To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>>>>>> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; edk2-devel@lists.01.org;
>>>>>>> afish@apple.com; Gao, Liming <liming.gao@intel.com>; Kinney, Michael
>>>>>>> D <michael.d.kinney@intel.com>
>>>>>>> Subject: Re: [edk2] [PATCH v3 1/5] MdeModulePkg: introduce non-
>>>>>>> discoverable device protocol
>>>>>>>
>>>>>>>> On Wed, Nov 16, 2016 at 04:59:27PM +0000, Ard Biesheuvel wrote:
>>>>>>>> Introduce a protocol that can be exposed by a platform for devices
>>>>>>>> that are not discoverable, usually because they are wired straight
>>>>>>>> to the memory bus rather than to an enumerable bus like PCI or USB.
>>>>>>>>
>>>>>>>> Contributed-under: TianoCore Contribution Agreement 1.0
>>>>>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>>>>>>> ---
>>>>>>>> MdeModulePkg/Include/Protocol/NonDiscoverableDevice.h | 90
>>>>>>> ++++++++++++++++++++
>>>>>>>> MdeModulePkg/MdeModulePkg.dec                         |  3 +
>>>>>>>> 2 files changed, 93 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/MdeModulePkg/Include/Protocol/NonDiscoverableDevice.h
>>>>>>>> b/MdeModulePkg/Include/Protocol/NonDiscoverableDevice.h
>>>>>>>> new file mode 100644
>>>>>>>> index 000000000000..47ed841b407b
>>>>>>>> --- /dev/null
>>>>>>>> +++ b/MdeModulePkg/Include/Protocol/NonDiscoverableDevice.h
>>>>>>>> @@ -0,0 +1,90 @@
>>>>>>>> +/** @file
>>>>>>>> +  Protocol to describe devices that are not on a discoverable bus
>>>>>>>> +
>>>>>>>> +  Copyright (c) 2016, Linaro, Ltd. All rights reserved.<BR>
>>>>>>>> +
>>>>>>>> +  This program and the accompanying materials  are licensed and
>>>>>>>> + made available under the terms and conditions of the BSD License
>>>>>>>> + which accompanies this distribution.  The full text of the license
>>>>>>>> + may be found at  http://opensource.org/licenses/bsd-license.php
>>>>>>>> +
>>>>>>>> +  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS
>>>>> IS"
>>>>>>>> + BASIS,  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND,
>>>>>>> EITHER EXPRESS OR IMPLIED.
>>>>>>>> +
>>>>>>>> +**/
>>>>>>>> +
>>>>>>>> +#ifndef __NON_DISCOVERABLE_DEVICE_H__ #define
>>>>>>>> +__NON_DISCOVERABLE_DEVICE_H__
>>>>>>>> +
>>>>>>>> +#include <IndustryStandard/Acpi.h>
>>>>>>>> +
>>>>>>>> +#define EDKII_NON_DISCOVERABLE_DEVICE_PROTOCOL_GUID \
>>>>>>>> +  { 0x0d51905b, 0xb77e, 0x452a, {0xa2, 0xc0, 0xec, 0xa0, 0xcc,
>>>>>>>> +0x8d, 0x51, 0x4a } }
>>>>>>
>>>>>> 1. Can you add "PCI" keyword into the protocol name?
>>>>>> e.g.: EDKII_NON_DISCOVERABLE_PCI_DEVICE_PROTOCOL_GUID
>>>>>>
>>>>>
>>>>> No. This protocol does not describe pci devices, and it is a peculiarity of the
>>>>> edk2 driver stack that some non-pci devices can only be driven by pci drivers.
>>>>>
>>>>> in other words, pci is part of the /driver/ side, and it is perfectly possible for,
>>>>> e.g., a non-discoverable ahci device to be driven by a different non-pci driver
>>>>> in the future.
>>>>>
>>>>
>>>> I see. So some types of devices are handled by the current
>>>> NonDiscoveablePciDevice driver, and some other types of devices may be
>>>> handled by a future NonDiscoverableXXXDevice driver.
>>>> Now since the AHCI type is already handled by the NonDiscoverablePciDevice
>>>> driver, when there is a new NonDiscoverableXXXDevice driver, how can the two
>>>> know whether it should manage the AHCI type device or not?
>>>
>>>Good question. But how does the UEFI driver model deal with that? What happens if i have two drivers that both support
>the
>>>Ahci Pci class codes?
>> PCI CFG header contains VendorID/DeviceID fields which can be used to distinguish
>> them.
>>
>
>No, that is not what I mean.
>
>Your question is how we should deal with multiple drivers that
>support, for instance, the AHCI non-discoverable device type. My
>answer is that this is not any different from a platform configuration
>that has more than one PCI I/O based driver that supports the AHCI PCI
>class codes. The UEFI driver model has priority rules and protocols to
>decide which driver gets precedence. I don't see how it should be any
>different here.

I see they are different. Based on PciIo, the *HCI drivers can query
additional information from PCI CFG header, instead of just using
the PCI class code.

But with the NonDiscoverableDevice protocol, there is no additional
information can help the *HCI drivers decide which to manage.

I don't see any practical negative point which prevents degrading
NonDiscoverableDevice protocol to NonDiscoverable*Pci*Protocol.
After all, as I said, all *HCI drivers are based on PciIo.

>
>Thanks,
>Ard.
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