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

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Date:	Tue, 23 Jul 2013 09:35:51 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	broonie@...nel.org,
	Sylwester Nawrocki <sylvester.nawrocki@...il.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	kyungmin.park@...sung.com, balbi@...com, jg1.han@...sung.com,
	s.nawrocki@...sung.com, kgene.kim@...sung.com,
	grant.likely@...aro.org, tony@...mide.com, arnd@...db.de,
	swarren@...dia.com, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-media@...r.kernel.org,
	linux-fbdev@...r.kernel.org, akpm@...ux-foundation.org,
	balajitk@...com, george.cherian@...com, nsekhar@...com,
	olof@...om.net, Stephen Warren <swarren@...dotorg.org>,
	b.zolnierkie@...sung.com,
	Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH 01/15] drivers: phy: add generic PHY framework

On Tue, Jul 23, 2013 at 09:58:34PM +0530, Kishon Vijay Abraham I wrote:
> Hi Greg,
> 
> On Tuesday 23 July 2013 09:48 PM, Greg KH wrote:
> > On Tue, Jul 23, 2013 at 08:48:24PM +0530, Kishon Vijay Abraham I wrote:
> >> Hi,
> >>
> >> On Tuesday 23 July 2013 08:07 PM, Alan Stern wrote:
> >>> On Tue, 23 Jul 2013, Tomasz Figa wrote:
> >>>
> >>>> On Tuesday 23 of July 2013 09:29:32 Tomasz Figa wrote:
> >>>>> Hi Alan,
> >>>
> >>> Thanks for helping to clarify the issues here.
> >>>
> >>>>>> Okay.  Are PHYs _always_ platform devices?
> >>>>>
> >>>>> They can be i2c, spi or any other device types as well.
> >>>
> >>> In those other cases, presumably there is no platform data associated
> >>> with the PHY since it isn't a platform device.  Then how does the
> >>> kernel know which controller is attached to the PHY?  Is this spelled
> >>> out in platform data associated with the PHY's i2c/spi/whatever parent?
> .
> .
> <snip>
> .
> .
> >>
> >> 	static struct phy *phy_lookup(void *priv) {
> >> 		.
> >> 		.
> >> 		if (phy->priv==priv) //instead of string comparison, we'll use pointer
> >> 			return phy;
> >> 	}
> >>
> >> PHY driver should be like
> >> 	phy_create((dev, ops, pdata->info);
> >>
> >> The controller driver would do
> >> 	phy_get(dev, NULL, pdata->info);
> >>
> >> Now the PHY framework will check for a match of *priv* pointer and return the PHY.
> >>
> >> I think this should be possible?
> > 
> > Ick, no.  Why can't you just pass the pointer to the phy itself?  If you
> > had a "priv" pointer to search from, then you could have just passed the
> > original phy pointer in the first place, right?
> > 
> > The issue is that a string "name" is not going to scale at all, as it
> > requires hard-coded information that will change over time (as the
> > existing clock interface is already showing.)
> > 
> > Please just pass the real "phy" pointer around, that's what it is there
> > for.  Your "board binding" logic/code should be able to handle this, as
> > it somehow was going to do the same thing with a "name".
> 
> The problem is the board file won't have the *phy* pointer. *phy* pointer is
> created at a much later time when the phy driver is probed.

Ok, then save it then, as no one could have used it before then, right?

All I don't want to see is any "get by name/void *" functions in the
api, as that way is fragile and will break, as people have already
shown.

Just pass the real pointer around.  If that is somehow a problem, then
something larger is a problem with how board devices are tied together :)

thanks,

greg k-h
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