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

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Message-ID: <aNFFpUZek-k5YXls@kuha.fi.intel.com>
Date: Mon, 22 Sep 2025 15:48:37 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Mark Pearson <mpearson-lenovo@...ebb.ca>
Cc: Greg KH <gregkh@...uxfoundation.org>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: ucsi: Handle incorrect num_connectors
 capability

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?

thanks,

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

-- 
heikki