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

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

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.

Thanks,
Ard.