Re: Question about EHCI PCI/platform drivers

David Brownell wrote:
> On Tuesday 15 May 2007, Tzachi Perelstein wrote:
>> David Brownell wrote:
>>> On Sunday 13 May 2007, Tzachi Perelstein wrote:
>>>> Hello,
>>>>
>>>> I'm working on EHCI HC glue port for Marvell Orion SoC. The Orion has
>>>> a PCI/PCIE interfaces as well as an integrated USB controller.
>>>>
>>>> While looking at ehci-hcd.c it looks like there's some kind of dependency
>>>> between PCI_DRIVER and PLATFORM_DRIVER. I saw some previous threads
>>>> about the ehci-fsl.c regarding this issue, but I'm not sure I understand,
>>>> for example, why in module_init if pci_register_driver fails the platform
>>>> driver is unregistered? Shouldn't these two types of drivers be independent?
>>> If the platform has PCI but you can't register a PCI driver, it's
>>> quite broken.  How broken must a platform be before you fix those
>>> bugs, rather than expect drivers to work around them?
>> I have no problem with my PCI, it works just fine! Who said anything about
>> bugs workaround???
> 
> You -- by asking why a bug (pci_register_driver fails) should
> be handled differently (working around the failure).

Asking about some existing implementation does not necessarily mean one need a workaround.
I just wanted to better understand this dependency and perhaps improving it. That's all.

>> I was just wondering if there is a _real_ reason why *if* pci_register_driver
>> fails then the platform driver will be unregistered. Theoretically it could be that
>> PCI will fail but platform driver will work ok, so why unregistering it?? Why not
>> just dumping an error message and continuing??
> 
> No; "theoretically" pci_register_driver() has no reason to fail
> on a correctly working system.

I agree with that. However, the existing implementation _does_ handle this theoretical
pci_register_driver failure by unregistering the *platform* driver (?).
Besides arguing with me if I have a buggy PCI or not, you couldn't explain _why_ this
is the appropriate handling.

It's not that important, so you can just forget it.

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