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

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Message-Id: <384b208d-5866-4563-8d84-23342a8e3663@app.fastmail.com>
Date: Mon, 29 Sep 2025 16:01:04 -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



On Mon, Sep 29, 2025, at 3:35 PM, Greg KH wrote:
> On Mon, Sep 29, 2025 at 03:25:06PM -0400, Mark Pearson wrote:
>> Hi Heikki,
>> 
>> On Mon, Sep 22, 2025, at 8:48 AM, Heikki Krogerus wrote:
>> > On Fri, Sep 19, 2025 at 11:45:48AM -0400, Mark Pearson wrote:
>> >> 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.
>> >
>> > I don't think it's necessary in this case if the fw is really fixed.
>> > But what says Greg?
>> >
>> I don't think the Fixes tag makes sense either; and to confirm - this will be fixed in FW.
>> 
>> Greg - can we go ahead with this please?
>
> It's the merge window right now, I'll pick it up after -rc1 is out.
>
Sounds good - thanks!
Mark