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

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Message-Id: <0ac78125-a028-4d99-b106-d792d8660d0f@app.fastmail.com>
Date: Fri, 22 Aug 2025 08:54:22 -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 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.

Mark