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

[Kishon Vijay Abraham I <kishon@ti.com>]

Hi,

On Friday 19 July 2013 09:24 PM, Stephen Warren wrote:
> On 07/19/2013 12:36 AM, Kishon Vijay Abraham I wrote:
>> Hi,
>>
>> On Friday 19 July 2013 11:59 AM, Greg KH wrote:
>>> On Fri, Jul 19, 2013 at 11:25:44AM +0530, Kishon Vijay Abraham I wrote:
>>>> 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.
>>>
>>> How does a consumer know which "label" to use in a non-dt system if
>>> there are multiple PHYs in the system?
>>
>> That should be passed using platform data.
>
> I don't think that's right. That's just like passing clock names in
> platform data, which I believe is frowned upon.
>
> Instead, why not take the approach that e.g. regulators have taken? Each
> driver defines the names of the objects that it requires. There is a
> table (registered by a board file) that has lookup key (device name,

We were using a similar approach with USB PHY layer but things started 
breaking after the device names are created using PLATFORM_DEVID_AUTO. 
Now theres no way to reliably know the device names in advance.
Btw I had such device name binding in my v3 of this patch series [1] and 
had some discussion with Grant during that time [2].

[1] -> 
http://archive.arm.linux.org.uk/lurker/message/20130320.091200.721a6fb5.hu.html
[2] -> https://lkml.org/lkml/2013/4/22/26

Thanks
Kishon