Re: [PATCH v2 1/5] MdeModulePkg: introduce non-discoverable device protocol

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

On 15 November 2016 at 08:31, Ni, Ruiyu <ruiyu.ni@intel.com> wrote:
> Ard,
>
> For the below protocol structure, it assumes that the non-discoverable
> PCI device contains only one BAR and the type is limited to USB/AHCI/SD/UFS/NVME
> devices.

For now, yes. It is quite unusual for such non-enumerable devices to
have several MMIO ranges (and I/O ranges do not exist at all on many
architectures, except when dealing with real PCI devices where the
root complex takes care of the I/O to MMIO translation)

> Could we have more types of such kind of device in future?

Yes. I actually added AMBA as well, because those devices have a
standardized identification register

> Could we have a device that contains multiple BAR?

Perhaps others could chime in here? The only example of mutiple BARs
would be multiple SDHCI slots on the same controller, but those could
easily be modeled as separate controllers as well, since they are
completely independent.

> Could we have a device that contains one BAR but the BAR size is non-default size?
>

Another good question. I think the best way for now is to extend the
protocol to allow it, but only add support to the helper library when
the need arises.

> I am asking all about this is because I am thinking would it be more flexible to have
> platform provide a ACPI resource descriptors and the NonDiscoverableDxe driver
> converts the ACPI resource descriptors to PCI BARs?
>
> You could refer to PciIo.GetBarAttributes() to see how one ACPI resource descriptor
> is created for one BAR.
>
> But please ignore my such concern if there is a spec to describe such non-discoverable
> PCI device.
>

No, there is no such spec, and I think your suggestion is very good. I
will investigate.

Thanks,
Ard.