Pointers for writing a good PCIe driver

[Mason]

On 17/02/2017 15:38, Bjorn Helgaas wrote:

> On Fri, Feb 17, 2017 at 10:20:20AM +0100, Mason wrote:
>
>> There might be some kind of misunderstanding.
>>
>> I don't plan to write a driver for a device that plugs into a PCIe slot.
>>
>> I intend to write a driver for the PCIe controller itself, which is
>> embedded in the SoC. (In order to support different types of PCIe
>> devices, with their respective drivers already upstream.)
>>
>> I think the controller driver belongs in drivers/pci/host ?
> 
> Sorry, I indeed misunderstood you.
> 
> The native PCI host controller drivers indeed live in
> drivers/pci/host/.
> 
> I don't know anything about your hardware or environment, but I highly
> encourage you to use ACPI (drivers/acpi/pci_root.c, with a little bit
> of arch support) or generic DT (drivers/pci/host/pci-host-generic.c)
> instead of writing a custom host controller driver.
> 
> The native drivers in drivers/pci/host are a huge maintenance hassle
> for no real benefit.

My SoC is built around an ARM Cortex A9.
I don't think (?) this platform has any support for ACPI.

I'm currently using this DT description:
http://lxr.free-electrons.com/source/arch/arm/boot/dts/tango4-common.dtsi

The "legacy" driver sits at ~700 lines. It would be awesome to be able
to discard all of it, and rely on generic upstream code. But I don't
understand how it is possible for a generic driver to support whatever
crazy solution some random vendor has come up with?

Regards.