Re: [PATCH v1 1/1] mux: mux-intel-usb: Add Intel USB Multiplexer driver

[sathyanarayanan kuppuswamy]

Hi,


On 05/31/2017 11:27 AM, Hans de Goede wrote:
> Hi,
>
> On 31-05-17 17:30, Peter Rosin wrote:
> > On 2017-05-31 16:18, Hans de Goede wrote:
> > > Hi,
> > >
> > > On 31-05-17 15:05, Peter Rosin wrote:
> > > > On 2017-05-31 14:21, Hans de Goede wrote:
> > > > > actually this is the first time I hear about a mux framework
> > > > > at all. Is there a git tree with the patches for this somewhere ?
> > > >
> > > > https://gitlab.com/peda-linux/mux.git in the "mux" branch.
> > > >
> > > > Series posted here:
> > > > https://lkml.org/lkml/2017/5/14/160
> > >
> > > Thank you.
> > >
> > > I see that mux_control_get() currently relies on devicetree describing
> > > the mux, that is not going to work on non devicetree platforms like
> > > x86 where the relation typically is not described ad all (*) ?
> >
> > Yes, I'm aware of this.
>
> Ok, good.
>
> > I wanted to keep things simple. Also, see
> > my reply on the other branch of this discussion.
> >
> > https://lkml.org/lkml/2017/5/31/58
> >
> > > Typically there would be a global list of mux_controls maintained
> > > by mux_[de]register and then mux_control_get() would walk this list
> > > until it finds a matching name. The names to register would then be
> > > passed in by platform data/code when registering and likewise the
> > > consumer would be passed a unique name to pass into mux_control_get()
> > > through platform data / code, would that work for you ?
> > >
> > > Note one option would be to set the names to use when registering
> > > a mux chip through device_properties, this is what the power-supply
> > > subsys is currently doing more or less.
> >
> > I had this lose plan to match by the struct device name, but if that
> > is not working the above seems fine too...
>
> There are 2 problems with using dev_name() :
>
> 1) dev_name() will be coupled to the mux_chip and one mux_chip may
> have multiple controllers (you could add a number postfix to work
> around this)
I think maintaining unique mux control names across all mux devices will be
bit difficult to maintain. Unless its auto created as Hans mentioned using
device name + chip index  + control index.

or , we can have unique names for mux-chips and get mux-control handles 
based
on index numbers. This should at least reduce some of the search time.

mux_control_get("mux chip name",  index)
> 2) The caller of mux_control_get() wants a fixed name, where as
> dev_name is not always fixed, e.g. with mux-chips which communicate
> via i2c it is something like 7-0064 where 7 is the i2c bus-number
> which depends on probe ordering and thus may not even be the same
> every boot.
>
> Regards,
>
> Hans

--
Sathyanarayanan Kuppuswamy
Linux kernel developer