Re: [PATCH v5 05/14] usb: typec: add API to get typec basic port power and data config

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

Hi Jun,

Sorry for the delay.

On Thu, May 17, 2018 at 02:41:31PM +0000, Jun Li wrote:
> Hi
> > -----Original Message-----
> > From: Heikki Krogerus [mailto:heikki.krogerus@linux.intel.com]
> > Sent: 2018??5??17?? 22:24
> > To: Jun Li <jun.li@nxp.com>
> > Cc: Mats Karrman <mats.dev.list@gmail.com>; robh+dt@kernel.org;
> > gregkh@linuxfoundation.org; linux@roeck-us.net; a.hajda@samsung.com;
> > cw00.choi@samsung.com; shufan_lee@richtek.com; Peter Chen
> > <peter.chen@nxp.com>; gsomlo@gmail.com; devicetree@vger.kernel.org;
> > linux-usb@vger.kernel.org; dl-linux-imx <linux-imx@nxp.com>
> > Subject: Re: [PATCH v5 05/14] usb: typec: add API to get typec basic port power
> > and data config
> > 
> > On Thu, May 17, 2018 at 02:05:41PM +0000, Jun Li wrote:
> > > Hi Heikki,
> > >
> > > > > I reread this patch and tried to see it more in the context of the
> > > > > other patches and the existing code. The naming of the existing
> > > > > string tables doesn't help in getting this right, however I have a proposal:
> > > > >
> > > > > typec_find_port_power_role() to get to TYPEC_PORT_SRC/SNK/DRP
> > > > > typec_find_port_data_role() to get to TYPEC_PORT_DFP/UFP/DRD
> > > > > typec_find_power_role() to get to TYPEC_SINK/SOURCE
> > > > >
> > > > > and sometime, if the use should arise
> > > > >
> > > > > typec_find_data_role() to get to TYPEC_DEVICE/HOST
> > > > >
> > > > > I think it is fairly comprehensible, *_port_* concerns a
> > > > > capability and without *_port_* it is an actual state. Plus it
> > > > > matches the names of the constants.
> > > >
> > > > Well, there are now four things to consider:
> > > >
> > > > 1) the roles (power and data) the port is capable of supporting
> > > > 2) Try.SRC and Try.SNK, i.e. the preferred role
> > > > 3) the current roles
> > > > 4) the role(s) the user want's to limit the use of a port with DRP
> > > > ports
> > > >
> > > > The last one I don't know if it's relevant with these functions.
> > > > It's not information that we would get for example from firmware.
> > > >
> > > > I also don't think we need to use these functions with the current
> > > > roles the port is in.
> > > >
> > > > If the preferred role is "sink" or "source", so just like the power
> > > > role, we don't need separate function for it here.
> > > >
> > > > So isn't two functions all we need here: one for the power and one
> > > > for data role?
> > >
> > > Take power as an example, can we use one function to only look up
> > > typec_port_types[]? as capability(typec_port_type) and
> > > state(typec_role) are different enum, and the allowed strings are different.
> > >
> > > static const char * const typec_roles[] = {
> > > 	[TYPEC_SINK]    = "sink",
> > > 	[TYPEC_SOURCE]  = "source",
> > > };
> > >
> > > static const char * const typec_port_types[] = {
> > > 	[TYPEC_PORT_SRC] = "source",
> > > 	[TYPEC_PORT_SNK] = "sink",
> > > 	[TYPEC_PORT_DRP] = "dual",
> > > };
> > 
> > Where out side the class code we need to convert the current role, the "state",
> > with these functions?
> 
> Currently, the only call site is getting the preferred power role from firmware.

My point was that if we used enum typec_port_type with the prefered
role, we could use the helper for power role with prefered role. But
never mind.


Thanks,

-- 
heikki