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

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Message-ID: <51E8D086.809@ti.com>
Date:	Fri, 19 Jul 2013 11:07:10 +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 Thursday 18 July 2013 09:19 PM, Greg KH wrote:
> On Thu, Jul 18, 2013 at 02:29:52PM +0530, Kishon Vijay Abraham I wrote:
>> Hi,
>>
>> On Thursday 18 July 2013 12:50 PM, Greg KH wrote:
>>> On Thu, Jul 18, 2013 at 12:16:10PM +0530, Kishon Vijay Abraham I wrote:
>>>> +struct phy_provider *__of_phy_provider_register(struct device *dev,
>>>> +	struct module *owner, struct phy * (*of_xlate)(struct device *dev,
>>>> +	struct of_phandle_args *args));
>>>> +struct phy_provider *__devm_of_phy_provider_register(struct device *dev,
>>>> +	struct module *owner, struct phy * (*of_xlate)(struct device *dev,
>>>> +	struct of_phandle_args *args))
>>>> +
>>>> +__of_phy_provider_register and __devm_of_phy_provider_register can be used to
>>>> +register the phy_provider and it takes device, owner and of_xlate as
>>>> +arguments. For the dt boot case, all PHY providers should use one of the above
>>>> +2 APIs to register the PHY provider.
>>>
>>> Why do you have __ for the prefix of a public function?  Is that really
>>> the way that OF handles this type of thing?
>>
>> I have a macro of_phy_provider_register/devm_of_phy_provider_register that
>> calls these functions and should be used by the PHY drivers. Probably I should
>> make a mention of it in the Documentation.
> 
> Yes, mention those as you never want to be calling __* functions
> directly, right?

correct.
> 
>>>> +	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.
> needed either.  Just stick to the pointer, it's easier, and safer that
> way.
> 
>>>> +static inline int phy_pm_runtime_get(struct phy *phy)
>>>> +{
>>>> +	if (WARN(IS_ERR(phy), "Invalid PHY reference\n"))
>>>> +		return -EINVAL;
>>>
>>> Why would phy ever not be valid and a error pointer?  And why dump the
>>> stack if that happens, that seems really extreme.
>>
>> hmm.. there might be cases where the same controller in one soc needs PHY
>> control and in some other soc does not need PHY control. In such cases, we
>> might get error pointer here.
>> I'll change WARN to dev_err.
> 
> I still don't understand.  You have control over the code that calls
> these functions, just ensure that they pass in a valid pointer, it's
> that simple.  Or am I missing something?

You are right. Valid pointer check can be done in controller code as well.

Thanks
Kishon
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