Hi Heikki, > -----Original Message----- > From: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx> > Sent: Friday, September 13, 2019 8:20 AM > To: Ajay Gupta <ajaykuee@xxxxxxxxx> > Cc: linux-usb@xxxxxxxxxxxxxxx; Ajay Gupta <ajayg@xxxxxxxxxx> > 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@xxxxxxxxxx> > > > > 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. Thanks > nvpublic > They always > make it difficult to modify the code later, and unfortunately we have them all > over the kernel. Look at the serial driver 8250_core/port/*.cas an example. > Ideally we should be able to "modularize" the whole alternate mode handling > in the ucsi driver since there are now two different ways the PPMs can handle > them instead of simply mixing the support for the new method straight into > the existing structures. > > thanks, > > -- > heikki
