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 19:04:45 +0530
From:	kishon <kishon@...com>
To:	Roger Quadros <rogerq@...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 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.

I'm not sure if that is what you are looking for :-P

Thanks
Kishon
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