linux-kernel - Re: [PATCH v4 1/2] platform/chrome: cros_ec

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACeCKacWhrZE6LFFwF=vDO8362u9feN71pPO8Qr8XoaRgwj5uw@mail.gmail.com>
Date:   Mon, 21 Aug 2023 16:30:36 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     "Patel, Utkarsh H" <utkarsh.h.patel@...el.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "heikki.krogerus@...ux.intel.com" <heikki.krogerus@...ux.intel.com>,
        "bleung@...omium.org" <bleung@...omium.org>
Subject: Re: [PATCH v4 1/2] platform/chrome: cros_ec_typec: Configure Retimer
 cable type

On Mon, Aug 21, 2023 at 10:18 AM Patel, Utkarsh H
<utkarsh.h.patel@...el.com> wrote:
>
> Hi Prashant,
>
> Thank you for the review.
>
> > -----Original Message-----
> > From: Prashant Malani <pmalani@...omium.org>
> > Sent: Friday, August 18, 2023 10:02 AM
> > To: Patel, Utkarsh H <utkarsh.h.patel@...el.com>
> > Cc: linux-kernel@...r.kernel.org; linux-usb@...r.kernel.org;
> > heikki.krogerus@...ux.intel.com; bleung@...omium.org
> > Subject: Re: [PATCH v4 1/2] platform/chrome: cros_ec_typec: Configure
> > Retimer cable type
> >
> > >  /*
> > >   * Spoof the VDOs that were likely communicated by the partner for TBT alt
> > >   * mode.
> > > @@ -432,6 +453,9 @@ static int cros_typec_enable_tbt(struct
> > > cros_typec_data *typec,
> > >
> > >     /* Cable Discover Mode VDO */
> > >     data.cable_mode = TBT_MODE;
> > > +
> > > +   data.cable_mode |= cros_typec_get_cable_vdo(port,
> > > +USB_TYPEC_TBT_SID);
> > > +

Here is the first call to cros_typec_get_cable_vdo(port, TBT)....

> > >     data.cable_mode |= TBT_SET_CABLE_SPEED(pd_ctrl->cable_speed);
> > >
> > >     if (pd_ctrl->control_flags & USB_PD_CTRL_OPTICAL_CABLE) @@ -
> > 522,8
> > > +546,10 @@ static int cros_typec_enable_usb4(struct cros_typec_data
> > *typec,
> > >     /* Cable Type */
> > >     if (pd_ctrl->control_flags & USB_PD_CTRL_OPTICAL_CABLE)
> > >             data.eudo |= EUDO_CABLE_TYPE_OPTICAL <<
> > EUDO_CABLE_TYPE_SHIFT;
> > > -   else if (pd_ctrl->control_flags & USB_PD_CTRL_ACTIVE_CABLE)
> > > +   else if (cros_typec_get_cable_vdo(port, USB_TYPEC_TBT_SID) &
> > > +TBT_CABLE_RETIMER)

And here is the 2nd.

> > >             data.eudo |= EUDO_CABLE_TYPE_RE_TIMER <<
> > EUDO_CABLE_TYPE_SHIFT;
> > We shouldn't need to call cros_typec_get_cable_vdo more than once. Either
> > call it once earlier when you are crafting the data.cable_mode member and
> > then re-use that variable here. Or don't call it there and just call it here.
>
> We are only calling it once depending upon which mode we enter TBT Alt or USB4.

There should only be 1 "call site" and that should be sufficient to
grab the VDO from the
framework for all circumstances. Whether the other invocation doesn't get called
under certain circumstances isn't as relevant.