Re: [Devel] Error in documentation of AcpiOsDerivePciId?

[Moore, Robert <robert.moore at intel.com>]

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Sorry, now to address your original question.

The AcpiOsDerivePciId interface was driven primarily by the needs of Linux, during the time that the Linux PCI-to-ACPI interaction was being designed and implemented.

I suspect that the ** was needed for the original implementation and then became obsolete later.

To my knowledge, we have never been asked to change the interface, so it has remained as-is.

Since AcpiOsDerivePciId is going to go away soon (we have the code running already), we will of course make the equivalent internal interface as simple as possible.

Bob


>-----Original Message-----
>From: devel-bounces(a)acpica.org [mailto:devel-bounces(a)acpica.org] On Behalf
>Of Moore, Robert
>Sent: Wednesday, August 04, 2010 2:37 PM
>To: Rudi
>Cc: devel(a)acpica.org
>Subject: Re: [Devel] Error in documentation of AcpiOsDerivePciId?
>
>Yes, there is a reason for ACPI_PCI_ID **.
>
From the ACPI Component Architecture User Guide and Programmer Reference:
>
>
>AcpiOsDerivePciId
>-----------------
>
>PciId
>
>Input: The full PCI ID (The full PCI configuration space address,
>consisting of a segment number, bus number, device number, and function
>number) as obtained from control methods within the BIOS ACPI tables.
>
>Output: Where the derived PCI ID is returned. Some or all of the PCI ID
>subfields may be updated by this function.
>
>
>
>This function derives a full PCI ID for a PCI device, consisting of a
>Segment number, a Bus number, and a Device number.
>
>The PCI hardware dynamically configures PCI bus numbers depending on the
>bus topology discovered during system initialization. The AcpiOsDerivePciId
>function is invoked by the ACPICA subsystem during configuration of a
>PCI_Config Operation Region in order to (possibly) update the Bus number in
>the PciId with the actual Bus number as determined by the hardware and
>operating system configuration.
>
>The PciId parameter is initially populated by the ACPICA subsystem during
>the Operation Region initialization. ACPICA then calls AcpiOsDerivePciId,
>which is expected to make any necessary modifications to the Segment, Bus,
>or Device number PCI ID subfields as appropriate for the current hardware
>and OS configuration.
>
>
>
>>-----Original Message-----
>>From: devel-bounces(a)acpica.org [mailto:devel-bounces(a)acpica.org] On Behalf
>>Of Rudi
>>Sent: Sunday, August 01, 2010 4:31 AM
>>Cc: devel(a)acpica.org
>>Subject: Re: [Devel] Error in documentation of AcpiOsDerivePciId?
>>
>>Hi all,
>>
>>is that still in the agenda ? Also, what is the reason why the last
>>parameter of AcpiOsDerivePciId() is "ACPI_PCI_ID **" and not just
>>"ACPI_PCI_ID *" ? Are there any situations, where AcpiOsDerivePciId
>>would want to reallocate PciId ?
>>
>>
>>
>>
>>Lin Ming wrote:
>>> 2010/4/22 Grégoire Sutre <gregoire.sutre(a)gmail.com>:
>>>> Hi Lin,
>>>>
>>>> Many thanks for your explanantion, I understand now why the second
>>>> argument passed to AcpiOsDerivePciId is a handle to the (PCI_Config)
>>>> operation region.
>>>>
>>>> But regarding the first argument of AcpiOsDerivePciId: the ACPICA
>>>> programmer reference says that: it is a handle to _the PCI device_.
>>>>
>>>> My question is: which PCI device?
>>>>
>>>> In my (possibly wrong) interpretation of the documentation, _the PCI
>>>> device_ is the device for which AcpiOsDerivePciId shall return an
>>>> updated Pci id.
>>>>
>>>> However, as far as I understand the code of AcpiEvPciConfigRegionSetup
>>>> (in file evrgnini.c), _the PCI device_ turns out to be an ancestor of
>>>> the device for which AcpiOsDerivePciId shall return an updated Pci id.
>>>> This ancestor being the upstream PCI root bridge (or the ACPI root node
>>>> if none was found).  This interpretation of _the PCI device_ is also
>>>> consistent with my understanding of the Linux implementation of
>>>> AcpiOsDerivePciId, which finds the updated PCI id by ``traversing'' the
>>>> PCI-to-PCI bridges that are on the branch from AcpiOsDerivePciId's
>first
>>>> argument to its second argument.
>>>
>>> You are right, the first argument is the PCI root node.
>>> We may need to update the doc to figure out this.
>>>
>>> Thanks,
>>> Lin Ming
>>> _______________________________________________
>>> Devel mailing list
>>> Devel(a)acpica.org
>>> http://lists.acpica.org/listinfo/devel
>>>
>>> To: gregoire.sutre(a)gmail.com
>>> Cc: devel(a)acpica.org
>>
>>--
>>
>>Ruediger "Rudi" Ihle
>>
>>"There's a fine line between wrong and visionary. Unfortunately
>> you have to be a visionary to see it." - Sheldon Cooper, Ph.D.
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