Re: [PATCH 01/15] drivers: phy: add generic PHY framework

[Kishon Vijay Abraham I]

Hi,

On Sunday 21 July 2013 04:01 PM, Tomasz Figa wrote:
> Hi,
>
> On Saturday 20 of July 2013 19:59:10 Greg KH wrote:
> > On Sat, Jul 20, 2013 at 10:32:26PM -0400, Alan Stern wrote:
> > > On Sat, 20 Jul 2013, Greg KH wrote:
> > > > > > > That should be passed using platform data.
> > > > > >
> > > > > > Ick, don't pass strings around, pass pointers.  If you have
> > > > > > platform
> > > > > > data you can get to, then put the pointer there, don't use a
> > > > > > "name".
> > > > >
> > > > > I don't think I understood you here :-s We wont have phy pointer
> > > > > when we create the device for the controller no?(it'll be done in
> > > > > board file). Probably I'm missing something.
> > > >
> > > > Why will you not have that pointer?  You can't rely on the "name" as
> > > > the device id will not match up, so you should be able to rely on
> > > > the pointer being in the structure that the board sets up, right?
> > > >
> > > > Don't use names, especially as ids can, and will, change, that is
> > > > going
> > > > to cause big problems.  Use pointers, this is C, we are supposed to
> > > > be
> > > > doing that :)
> > >
> > > Kishon, I think what Greg means is this:  The name you are using must
> > > be stored somewhere in a data structure constructed by the board file,
> > > right?  Or at least, associated with some data structure somehow.
> > > Otherwise the platform code wouldn't know which PHY hardware
> > > corresponded to a particular name.
> > >
> > > Greg's suggestion is that you store the address of that data structure
> > > in the platform data instead of storing the name string.  Have the
> > > consumer pass the data structure's address when it calls phy_create,
> > > instead of passing the name.  Then you don't have to worry about two
> > > PHYs accidentally ending up with the same name or any other similar
> > > problems.
> >
> > Close, but the issue is that whatever returns from phy_create() should
> > then be used, no need to call any "find" functions, as you can just use
> > the pointer that phy_create() returns.  Much like all other class api
> > functions in the kernel work.
>
> I think there is a confusion here about who registers the PHYs.
>
> All platform code does is registering a platform/i2c/whatever device,
> which causes a driver (located in drivers/phy/) to be instantiated. Such
> drivers call phy_create(), usually in their probe() callbacks, so
> platform_code has no way (and should have no way, for the sake of
> layering) to get what phy_create() returns.

right.
> IMHO we need a lookup method for PHYs, just like for clocks, regulators,
> PWMs or even i2c busses because there are complex cases when passing just
> a name using platform data will not work. I would second what Stephen said
> [1] and define a structure doing things in a DT-like way.
>
> Example;
>
> [platform code]
>
> static const struct phy_lookup my_phy_lookup[] = {
> 	PHY_LOOKUP("s3c-hsotg.0", "otg", "samsung-usbphy.1", "phy.2"),

The only problem here is that if *PLATFORM_DEVID_AUTO* is used while 
creating the device, the ids in the device name would change and 
PHY_LOOKUP wont be useful.

Thanks
Kishon
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