linux-kernel - Re: [REGRESSION] Missing bcm5974 touchpad on Macbooks

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Message-ID: <c2e4ae25-1e8a-4f54-8321-800a7b7f8583@gmail.com>
Date: Mon, 4 Mar 2024 15:04:26 +0100
From: Javier Carrasco <javier.carrasco.cruz@...il.com>
To: Takashi Iwai <tiwai@...e.de>,
 Javier Carrasco <javier.carrasco@...fvision.net>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>, linux-input@...r.kernel.org,
 linux-kernel@...r.kernel.org, regressions@...ts.linux.dev
Subject: Re: [REGRESSION] Missing bcm5974 touchpad on Macbooks


On 04.03.24 13:45, Takashi Iwai wrote:
> On Mon, 04 Mar 2024 12:26:48 +0100,
> Javier Carrasco wrote:
>>
>> On 04.03.24 09:35, Takashi Iwai wrote:
>>> Hi,
>>>
>>> we've received a few regression reports for openSUSE Leap about the
>>> missing touchpad on Macbooks.  After debugging, this turned out to be
>>> the backport of the commit 2b9c3eb32a699acdd4784d6b93743271b4970899
>>>     Input: bcm5974 - check endpoint type before starting traffic
>>>
>>> And, the same regression was confirmed on the upstream 6.8-rc6
>>> kernel.
>>>
>>> Reverting the commit above fixes the problem, the touchpad reappears.
>>>
>>> The detailed hardware info is found at:
>>>   https://bugzilla.suse.com/show_bug.cgi?id=1220030
>>>
>>> Feel free to join the bugzilla above, or let me know if you need
>>> something for debugging, then I'll delegate on the bugzilla.
>>>
>>>
>>> thanks,
>>>
>>> Takashi
>>>
>>
>> Hi Takashi,
>>
>> The commit adds a check to ensure that the endpoint type is interrupt.
>>
>> According to that report, the issue arose with a MacBook Pro 5.1 (no
>> button, only trackpad endpoint), so the check on the tp_ep address
>> (0x81) returns false. I assume that you see an error message
>> ("Unexpected non-int endpoint) and  the probe function fails returning
>> -ENODEV.
> 
> Right, there is the message.
> 
>> Do you see any warning in the logs when you revert the commit? It was
>> added to prevent using wrong endpoint types, which will display the
>> following warning: "BOGUS urb xfer, pipe "some_number" != type
>> "another_number""
> 
> The revert was tested on the downstream kernel, but it has also the
> check of bogus pipe, and there was no such warning, as far as I see
> the report.
> 
>> I am just wondering if for some reason the check on interrupt type is
>> wrong here.
> 
> I'll ask reporters to give the lsusb -v output so that we can take a
> deeper look.  Also, I'm building a test kernel based on 6.8-rc7 with
> the revert, and ask reporters to test with it, just to be sure.
> 
> 
> thanks,
> 
> Takashi


Getting the output of lsusb would be awesome, thank you.

The bcm9547 driver has always made the assumption that the endpoint type
is interrupt, and the expected output from lsusb would be something like

bEndpointAddress     0x81  EP 1 IN
bmAttributes         3
Transfer Type        Interrupt

which is what the reverted commit checks.

I don't have the specific piece of hardware the report mentions, but I
triggered the probe with the endpoint type = interrupt and the check was
fine i.e. the probe did not fail. That made me think that the endpoint
type could be different, but I am dubious about that.

I will keep an eye on the bugzilla you linked, in case we get feedback
quickly.

Best regards,
Javier Carrasco