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

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Date:	Fri, 19 Jul 2013 11:25:44 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	<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-discuss@...ts.ozlabs.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>
Subject: Re: [PATCH 01/15] drivers: phy: add generic PHY framework

Hi,

On Friday 19 July 2013 11:13 AM, Greg KH wrote:
> On Fri, Jul 19, 2013 at 11:07:10AM +0530, Kishon Vijay Abraham I wrote:
>>>>>> +	ret = dev_set_name(&phy->dev, "%s.%d", dev_name(dev), id);
>>>>>
>>>>> Your naming is odd, no "phy" anywhere in it?  You rely on the sender to
>>>>> never send a duplicate name.id pair?  Why not create your own ids based
>>>>> on the number of phys in the system, like almost all other classes and
>>>>> subsystems do?
>>>>
>>>> hmm.. some PHY drivers use the id they provide to perform some of their
>>>> internal operation as in [1] (This is used only if a single PHY provider
>>>> implements multiple PHYS). Probably I'll add an option like PLATFORM_DEVID_AUTO
>>>> to give the PHY drivers an option to use auto id.
>>>>
>>>> [1] ->
>>>> http://archive.arm.linux.org.uk/lurker/message/20130628.134308.4a8f7668.ca.html
>>>
>>> No, who cares about the id?  No one outside of the phy core ever should,
>>> because you pass back the only pointer that they really do care about,
>>> if they need to do anything with the device.  Use that, and then you can
>>
>> hmm.. ok.
>>
>>> rip out all of the "search for a phy by a string" logic, as that's not
>>
>> Actually this is needed for non-dt boot case. In the case of dt boot, we use a
>> phandle by which the controller can get a reference to the phy. But in the case
>> of non-dt boot, the controller can get a reference to the phy only by label.
> 
> I don't understand.  They registered the phy, and got back a pointer to
> it.  Why can't they save it in their local structure to use it again
> later if needed?  They should never have to "ask" for the device, as the

One is a *PHY provider* driver which is a driver for some PHY device. This will
use phy_create to create the phy.
The other is a *PHY consumer* driver which might be any controller driver (can
be USB/SATA/PCIE). The PHY consumer will use phy_get to get a reference to the
phy (by *phandle* in the case of dt boot and *label* in the case of non-dt boot).
> device id might be unknown if there are multiple devices in the system.

I agree with you on the device id part. That need not be known to the PHY driver.

Thanks
Kishon
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