linux-kernel - Re: [RFC PATCH 5/6] usb: otg: add device tree support to otg library

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Date:	Mon, 21 Jan 2013 16:23:29 +0200
From:	Roger Quadros <rogerq@...com>
To:	kishon <kishon@...com>
CC:	<devicetree-discuss@...ts.ozlabs.org>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-usb@...r.kernel.org>, <linux-sh@...r.kernel.org>,
	<linuxppc-dev@...ts.ozlabs.org>, <balbi@...com>,
	<grant.likely@...retlab.ca>, <rob.herring@...xeda.com>,
	<rob@...dley.net>, <b-cousson@...com>, <tony@...mide.com>,
	<linux@....linux.org.uk>, <horms@...ge.net.au>,
	<magnus.damm@...il.com>, <cbou@...l.ru>, <dwmw2@...radead.org>,
	<alexander.shishkin@...ux.intel.com>, <gregkh@...uxfoundation.org>,
	<leoli@...escale.com>, <eric.y.miao@...il.com>,
	<haojian.zhuang@...il.com>, <stern@...land.harvard.edu>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: Re: [RFC PATCH 5/6] usb: otg: add device tree support to otg library

On 01/21/2013 03:34 PM, kishon wrote:
> On Monday 21 January 2013 06:51 PM, Roger Quadros wrote:
>> On 01/16/2013 05:01 PM, Kishon Vijay Abraham I wrote:
>>> Added an API devm_usb_get_phy_by_phandle(), to get usb phy by passing a
>>> device node phandle value. This function will return a pointer to
>>> the phy on success, -EPROBE_DEFER if there is a device_node for the
>>> phandle,
>>> but the phy has not been added, or a ERR_PTR() otherwise.
>>>
>>> Cc: Marc Kleine-Budde <mkl@...gutronix.de>
>>> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
>>> ---
>>>   drivers/usb/otg/otg.c   |   77
>>> +++++++++++++++++++++++++++++++++++++++++++++++
>>>   include/linux/usb/phy.h |    8 +++++
>>>   2 files changed, 85 insertions(+)
>>>
>>> diff --git a/drivers/usb/otg/otg.c b/drivers/usb/otg/otg.c
>>> index dbf2043..e9799bb 100644
>>> --- a/drivers/usb/otg/otg.c
>>> +++ b/drivers/usb/otg/otg.c
>>> @@ -13,7 +13,9 @@
>>>   #include <linux/export.h>
>>>   #include <linux/err.h>
>>>   #include <linux/device.h>
>>> +#include <linux/module.h>
>>>   #include <linux/slab.h>
>>> +#include <linux/of.h>
>>>
>>>   #include <linux/usb/otg.h>
>>>
>>> @@ -34,6 +36,20 @@ static struct usb_phy *__usb_find_phy(struct
>>> device *dev, u8 index)
>>>       return ERR_PTR(-ENODEV);
>>>   }
>>>
>>> +static struct usb_phy *__of_usb_find_phy(struct device_node *node)
>>> +{
>>> +    struct usb_phy  *phy;
>>> +
>>> +    list_for_each_entry(phy, &phy_list, head) {
>>> +        if (node != phy->dev->of_node)
>>> +            continue;
>>> +
>>> +        return phy;
>>> +    }
>>> +
>>> +    return ERR_PTR(-ENODEV);
>>> +}
>>> +
>>>   static void devm_usb_phy_release(struct device *dev, void *res)
>>>   {
>>>       struct usb_phy *phy = *(struct usb_phy **)res;
>>> @@ -109,6 +125,67 @@ err0:
>>>   }
>>>   EXPORT_SYMBOL(usb_get_phy);
>>>
>>> + /**
>>> + * devm_usb_get_phy_by_phandle - find the USB PHY by phandle
>>> + * @dev - device that requests this phy
>>> + * @phandle - name of the property holding the phy phandle value
>>> + * @index - the index of the phy
>>> + *
>>> + * Returns the phy driver associated with the given phandle value,
>>> + * after getting a refcount to it, -ENODEV if there is no such phy or
>>> + * -EPROBE_DEFER if there is a phandle to the phy, but the device is
>>> + * not yet loaded. While at that, it also associates the device with
>>> + * the phy using devres. On driver detach, release function is invoked
>>> + * on the devres data, then, devres data is freed.
>>> + *
>>> + * For use by USB host and peripheral drivers.
>>> + */
>>> +struct usb_phy *devm_usb_get_phy_by_phandle(struct device *dev,
>>> +    const char *phandle, u8 index)
>>> +{
>>> +    struct usb_phy    *phy = NULL, **ptr;
>>> +    unsigned long    flags;
>>> +    struct device_node *node;
>>> +
>>> +    if (!dev->of_node) {
>>> +        dev_dbg(dev, "device does not have a device node entry\n");
>>> +        return ERR_PTR(-EINVAL);
>>> +    }
>>> +
>>> +    node = of_parse_phandle(dev->of_node, phandle, index);
>>> +    if (!node) {
>>> +        dev_dbg(dev, "failed to get %s phandle in %s node\n", phandle,
>>> +            dev->of_node->full_name);
>>> +        return ERR_PTR(-ENODEV);
>>> +    }
>>> +
>>> +    ptr = devres_alloc(devm_usb_phy_release, sizeof(*ptr), GFP_KERNEL);
>>> +    if (!ptr) {
>>> +        dev_dbg(dev, "failed to allocate memory for devres\n");
>>> +        return ERR_PTR(-ENOMEM);
>>> +    }
>>
>> I fail to understand why you need ptr at all and why do devres_alloc()
>> for it.
> 
> Thats how we create a "managed device resource". You can have a look at
> Documentation/driver-model/devres.txt and drivers/base/devres.c.

OK, I get it now. You might want to update the text file too since you
are adding a automagically managed interface.

regards,
-roger
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