Re: [RFC PATCH] USB:XHCI:skip hub registration

From: liulongfang
Date: Fri Apr 16 2021 - 23:11:17 EST

On 2021/4/16 23:20, Alan Stern wrote:
> On Fri, Apr 16, 2021 at 10:03:21AM +0800, liulongfang wrote:
>> On 2021/4/15 22:43, Alan Stern wrote:
>>> On Thu, Apr 15, 2021 at 08:22:38PM +0800, Longfang Liu wrote:
>>>> When the number of ports on the USB hub is 0, skip the registration
>>>> operation of the USB hub.
>>>> The current Kunpeng930's XHCI hardware controller is defective. The number
>>>> of ports on its USB3.0 bus controller is 0, and the number of ports on
>>>> the USB2.0 bus controller is 1.
>>>> In order to solve this problem that the USB3.0 controller does not have
>>>> a port which causes the registration of the hub to fail, this patch passes
>>>> the defect information by adding flags in the quirks of xhci and usb_hcd,
>>>> and finally skips the registration process of the hub directly according
>>>> to the results of these flags when the hub is initialized.
>>>> Signed-off-by: Longfang Liu <liulongfang@xxxxxxxxxx>
>>> The objections that Greg raised are all good ones.
>>> But even aside from them, this patch doesn't actually do what the
>>> description says. The patch doesn't remove the call to usb_add_hcd
>>> for the USB-3 bus. If you simply skipped that call (and the
>>> corresponding call to usb_remove_hcd) when there are no
>>> ports on the root hub, none of the stuff in this patch would be needed.
>>> Alan Stern
>> "[RFC PATCH] USB:XHCI:Adjust the log level of hub"
> I don't understand. What patch is that? Do you have a URL for it?

>> The current method is an improved method of the above patch.
>> This patch just make it skip registering USB-3 root hub if that hub has no ports,
> No, that isn't what this patch does.
> If the root hub wasn't registered, hub_probe wouldn't get called. But
> with your patch, the system tries to register the root hub, and it does
> call hub_probe, and then that function fails with a warning message.
> The way to _really_ akip registering the root hub is to change the
> xhci-hcd code. Make it skip calling usb_add_hcd.
>> after skipping registering, no port will not report error log,the goal of this
>> patch is reached without error log output.
> Why do you want to get rid of the error log output? There really _is_
> an error, because the USB-3 hardware on your controller is defective.
> Since the hardware is buggy, we _should_ print an error message in the
> kernel log.
> Alan Stern
> .