linux-kernel - Re: [PATCH 2/6] phy: improved lookup method

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Message-ID: <20140923105311.GB18814@xps8300>
Date:	Tue, 23 Sep 2014 13:53:11 +0300
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...com>,
	Vivek Gautam <gautam.vivek@...sung.com>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 2/6] phy: improved lookup method

On Mon, Sep 22, 2014 at 05:07:55PM +0530, Kishon Vijay Abraham I wrote:
> On Thursday 18 September 2014 03:55 PM, Heikki Krogerus wrote:
> > On Mon, Sep 15, 2014 at 03:35:08PM +0300, Heikki Krogerus wrote:
> >> On Fri, Sep 12, 2014 at 08:16:01PM +0530, Kishon Vijay Abraham I wrote:
> >>> Assume you have 2 phys in your system..
> >>> static struct phy_lookup usb_lookup = {
> >>> 	.phy_name	= "phy-usb.0",
> >>> 	.dev_id		= "usb.0",
> >>> 	.con_id		= "usb",
> >>> };
> >>>
> >>> static struct phy_lookup sata_lookup = {
> >>> 	.phy_name	= "sata-usb.1",
> >>> 	.dev_id		= "sata.0",
> >>> 	.con_id		= "sata",
> >>> };
> >>>
> >>> First you do modprobe phy-usb, the probe of USB PHY driver gets invoked and it
> >>> creates the PHY. The phy-core will find a free id (now it will be 0) and then
> >>> name the phy as phy-usb.0.
> >>> Then with modprobe phy-sata, the phy-core will create phy-sata.1.
> >>>
> >>> This is an ideal case where the .phy_name in phy_lookup matches.
> >>>
> >>> Consider if the order is flipped and the user does modprobe phy-sata first. The
> >>> phy_names won't match anymore (the sata phy device name would be "sata-usb.0").
> > 
> > Actually, I don't think there would be this problem if we used the
> > name of the actual device which is the parent of phy devices, right?
> 
> hmm.. but if the parent is a multi-phy phy provider (like pipe3 PHY driver), we
> might end up with the same problem.

I'm not completely sure what you mean? If you are talking about
platforms with multiple instances of a single phy, I don't see how
there could ever be a scenario where we did not know the order in
which they were enumerated. Can you give an example again?


Thanks,

-- 
heikki
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