linux-kernel - Re: [PATCH v4 1/6] drivers: phy: add generic PHY framework

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Date:	Wed, 3 Apr 2013 11:02:39 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	<linux-usb@...r.kernel.org>, <mchehab@...hat.com>,
	<linux-doc@...r.kernel.org>, <tony@...mide.com>,
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	<eballetbo@...il.com>, <devicetree-discuss@...ts.ozlabs.org>,
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	<akpm@...ux-foundation.org>, <davem@...emloft.net>
Subject: Re: [PATCH v4 1/6] drivers: phy: add generic PHY framework

On Tuesday 02 April 2013 09:10 PM, Stephen Warren wrote:
> On 04/02/2013 02:37 AM, Kishon Vijay Abraham I wrote:
>> Hi,
>>
>> On Thursday 28 March 2013 09:15 PM, Stephen Warren wrote:
>>> On 03/27/2013 11:43 PM, Kishon Vijay Abraham I wrote:
>>>> The PHY framework provides a set of APIs for the PHY drivers to
>>>> create/destroy a PHY and APIs for the PHY users to obtain a reference
>>>> to the
>>>
>>>> diff --git a/Documentation/devicetree/bindings/phy/phy-bindings.txt
>
>>>> +PHY subsystem refer Documentation/phy.txt
>>>> +
>>>> +PHY device node
>>>> +===============
>>>> +
>>>> +Optional Properties:
>>>> +#phy-cells:    Number of cells in a PHY specifier;  The meaning of all those
>>>> +        cells is defined by the binding for the phy node. However
>>>> +        in-order to return the correct PHY, the PHY susbsystem
>>>> +        requires the first cell always refers to the port.
>>>
>>> Why impose that restriction? Other DT bindings do not.
>>>
>>> This is typically implemented by having each provider driver implement a
>>> .of_xlate() operation, which parses all of the specifier cells, and
>>> returns the ID of the object it represents. This allows bindings to use
>>> whatever arbitrary representation they want.
>>
>> Do you mean something like this
>>
>> struct phy *of_phy_get(struct device *dev, int index)
>> {
>>      struct phy *phy = NULL;
>>      struct phy_bind *phy_map = NULL;
>>      struct of_phandle_args args;
>>      struct device_node *node;
>>
>>      if (!dev->of_node) {
>>          dev_dbg(dev, "device does not have a device node entry\n");
>>          return ERR_PTR(-EINVAL);
>>      }
>>
>>      ret = of_parse_phandle_with_args(dev->of_node, "phys", "#phy-cells",
>>          index, &args);
>>      if (ret) {
>>          dev_dbg(dev, "failed to get phy in %s node\n",
>>              dev->of_node->full_name);
>>          return ERR_PTR(-ENODEV);
>>      }
>
> Looks good.
>
>> //Here we have to get a reference to the phy in order to call of_xlate
>> which seems a little hacky to me. I'm not sure how else can we call the
>> provider driver :-(
>>      phy = of_phy_lookup(dev, node);
>>      if (IS_ERR(phy) || !try_module_get(phy->ops->owner)) {
>>          phy = ERR_PTR(-EPROBE_DEFER);
>>          goto err0;
>>      }
>
> I think the concept of a "PHY provider" and a "PHY instance" are different.
>
> of_xlate should be called on a "PHY provider", and return a "PHY
> instance". Hence, above you want to only look up a "PHY provider", so
> there's no hackiness involved.

Cool. That makes it a lot clearer.

Thanks
Kishon
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