linux-kernel - Re: [PATCH 4/5] arm: omap3: twl: use the new lookup method with usb phy

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Message-ID: <20131216144314.GB22944@xps8300>
Date:	Mon, 16 Dec 2013 16:43:14 +0200
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH 4/5] arm: omap3: twl: use the new lookup method with usb
 phy

Hi,

On Mon, Dec 16, 2013 at 04:34:35PM +0530, Kishon Vijay Abraham I wrote:
> On Monday 09 December 2013 08:38 PM, Heikki Krogerus wrote:
> > Provide a complete association for the phy and it's user
> > (musb) with the new phy_lookup_table.
> > 
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> > ---
> >  arch/arm/mach-omap2/twl-common.c | 15 ++++++---------
> >  1 file changed, 6 insertions(+), 9 deletions(-)
> > 
> > diff --git a/arch/arm/mach-omap2/twl-common.c b/arch/arm/mach-omap2/twl-common.c
> > index b0d54da..972430b 100644
> > --- a/arch/arm/mach-omap2/twl-common.c
> > +++ b/arch/arm/mach-omap2/twl-common.c
> > @@ -91,18 +91,13 @@ void __init omap_pmic_late_init(void)
> >  }
> >  
> >  #if defined(CONFIG_ARCH_OMAP3)
> > -struct phy_consumer consumers[] = {
> > -	PHY_CONSUMER("musb-hdrc.0", "usb"),
> > -};
> > -
> > -struct phy_init_data init_data = {
> > -	.consumers = consumers,
> > -	.num_consumers = ARRAY_SIZE(consumers),
> > +static struct phy_lookup_table twl4030_usb_lookup = {
> > +	.dev_id = "musb-hdrc.0",
> > +	.table = PHY_LOOKUP("phy-twl4030_usb.0", NULL),
> >  };
> 
> had a similar approach during the initial version of phy framework [1] (see
> phy_bind) but changed it later [2] . Here you should know the device names of
> two devices and even if one of them started using DEVID_AUTO, it'll start
> breaking. Such an approach needs to reviewed carefully.

If somebody creates a regression by changing something like the
platform device id without checking all the users, he deserves to get
into big trouble. I don't see why an individual framework should
provide protection against such cases.

In any case, having two device names to deal with does not add any
more risk. These associations should always be made in the place where
the phy device is created so you will always know it's device name.
Normally the platform code creates these associations in the same
place it creates the platform devices, so you definitely know what the
device names will be.

In this case it's actually created in drivers/mfd/twl-core.c, so I do
need to update this and move the lookup table there. We can still
deliver the user name as platform data, though I believe it's always
"musb". Maybe we could actually skip that and just hard code the name?
The name of the phy we will of course know as the platform device is
created there and then, so the two device names don't create any more
risk even in this case.

Thanks,

-- 
heikki
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