Re: [PATCH v5] usb: typec: ucsi: add support for separate DP altmode devices

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Tue, Sep 17, 2019 at 09:41:49PM +0000, Ajay Gupta wrote:
> Hi Heikki,
> 
> > -----Original Message-----
> > From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > Sent: Friday, September 13, 2019 8:20 AM
> > To: Ajay Gupta <ajaykuee@gmail.com>
> > Cc: linux-usb@vger.kernel.org; Ajay Gupta <ajayg@nvidia.com>
> > Subject: Re: [PATCH v5] usb: typec: ucsi: add support for separate DP altmode
> > devices
> > 
> > Hi Ajay,
> > 
> > On Fri, Sep 06, 2019 at 09:55:16AM -0700, Ajay Gupta wrote:
> > > From: Ajay Gupta <ajayg@nvidia.com>
> > >
> > > CCGx controller used on NVIDIA GPU card has two separate display
> > > altmode for two DP pin assignments. UCSI specification doesn't
> > > prohibits using separate display altmode.
> > >
> > > Current UCSI Type-C framework expects only one display altmode for all
> > > DP pin assignment. This patch squashes two separate display altmode
> > > into single altmode to support controllers with separate display
> > > altmode. We first read all the alternate modes of connector and then
> > > run through it to know if there are separate display altmodes. If so,
> > > it prepares a new port altmode set after squashing two or more
> > > separate altmodes into one.
> > 
> > I'm going to go over this one more time during the merge window. I have an
> > idea how to improve this. Please bear with me. I have to make sure all options
> > were considered.
> > 
> > I'm really sorry to block this for so long, but I'm just really really afraid of
> > mixing special case solutions like this into otherwise generic code.
> 
> I can update the patch to make sure generic code flow remains as-is and special
> case is executed only for UCSI controllers which needs squashing of duplicate
> DP altmodes.
> We can use the new function pointer update_altmode() added in "struct ucsi_ppm" in v5
> of my patch for this purpose.
> 
> if (recipient == UCSI_RECIPIENT_CON && ucsi->ppm && ucsi->ppm->update_altmodes)
> 	Get all the altmodes first, pass it to update_altmodes() for squashing if needed,
> 	and then register each altmodes.
> else
> 	Use the current method where we get and register one altmode at a time.
> 
> Please let me know if this looks fine to you.

No. Please wait. I'm refactoring ucsi.c. I'm going to redo the I/O
completely, and also do some long waited cleanups. Those changes
should make handling this case also much easier.

thanks,

-- 
heikki