linux-kernel - Re: [PATCH] usb: typec: ucsi: Handle incorrect num

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Message-Id: <1c185541-2b6b-4c43-938a-9f4f4d1499b4@app.fastmail.com>
Date: Wed, 17 Sep 2025 14:14:28 -0400
From: "Mark Pearson" <mpearson-lenovo@...ebb.ca>
To: "Greg KH" <gregkh@...uxfoundation.org>
Cc: "Heikki Krogerus" <heikki.krogerus@...ux.intel.com>,
 linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: ucsi: Handle incorrect num_connectors capability

Hi all,

On Fri, Aug 22, 2025, at 8:54 AM, Mark Pearson wrote:
> Hi Greg,
>
> On Fri, Aug 22, 2025, at 12:51 AM, Greg KH wrote:
>> On Thu, Aug 21, 2025 at 02:53:07PM -0400, Mark Pearson wrote:
>>> The UCSI spec states that the num_connectors field is 7 bits, and the
>>> 8th bit is reserved and should be set to zero.
>>> Some buggy FW has been known to set this bit, and it can lead to a
>>> system not booting.
>>> Flag that the FW is not behaving correctly, and auto-fix the value
>>> so that the system boots correctly.
>>> 
>>> Found on Lenovo P1 G8 during Linux enablement program. The FW will
>>> be fixed, but seemed worth addressing in case it hit platforms that
>>> aren't officially Linux supported.
>>> 
>>> Signed-off-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
>>
>> Any hints as to what commit id this fixes?
>>
>> thanks,
>>
>> greg k-h
>
> Maybe 3cf657f ('Remove all bit-fields')?
>
> The commit there states that 'We can't use bit fields with data that is 
> received or send
> to/from the device.'
> Not sure why that is, but I assumed this means we shouldn't change the 
> structure to use 7 bits for num_connectors, which was my original plan.
>
> After that, we go all the way back to the file creation (c1b0bc2) where 
> it was defined as 8 bit.
>

Just a gentle nudge to see if there are any concerns or questions with the patch.

Thanks
Mark