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

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Message-Id: <84064f76-bc99-4f3c-b26b-0dacf3632279@app.fastmail.com>
Date: Fri, 19 Sep 2025 11:45:48 -0400
From: "Mark Pearson" <mpearson-lenovo@...ebb.ca>
To: "Heikki Krogerus" <heikki.krogerus@...ux.intel.com>,
 "Greg KH" <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: ucsi: Handle incorrect num_connectors capability

Hi Heikki,

On Fri, Sep 19, 2025, at 3:44 AM, Heikki Krogerus wrote:
> On Thu, Sep 18, 2025 at 09:50:30AM +0200, Greg KH wrote:
>> On Wed, Sep 17, 2025 at 02:14:28PM -0400, Mark Pearson wrote:
>> > 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.
>> 
>> I was waiting for the maintainer of this code to review it :)
>
> So not Fixes tag?
>

I can add a Fixes tag for the very original commit of this file (c1b0bc2) if that's wanted.

> Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
>
Thanks for the review

Mark