linux-kernel - Re: [PATCH v2 2/2] usb: ulpi: Call of_node

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Date:   Tue, 25 Jan 2022 11:53:58 -0500
From:   Sean Anderson <sean.anderson@...o.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] usb: ulpi: Call of_node_put correctly

Hi Heikki,

On 1/25/22 4:18 AM, Heikki Krogerus wrote:
> On Mon, Jan 24, 2022 at 12:33:44PM -0500, Sean Anderson wrote:
>> of_node_put should always be called on device nodes gotten from
>> of_get_*. Additionally, it should only be called after there are no
>> remaining users. To address the first issue, call of_node_put if later
>> steps in ulpi_register fail. To address the latter, call of_node_put
>> only after calling device_unregister.
> 
> This looks like a fix, but you don't have the fix tag.

You're right this should have

Fixes: ef6a7bcfb01c ("usb: ulpi: Support device discovery via DT")

>> Signed-off-by: Sean Anderson <sean.anderson@...o.com>
>> ---
>> 
>> Changes in v2:
>> - New
>> 
>>  drivers/usb/common/ulpi.c | 10 +++++++---
>>  1 file changed, 7 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
>> index 87deb514eb78..c6ba72544f2b 100644
>> --- a/drivers/usb/common/ulpi.c
>> +++ b/drivers/usb/common/ulpi.c
>> @@ -301,11 +301,11 @@ static int ulpi_register(struct device *dev, struct ulpi *ulpi)
>>  
>>  	ret = ulpi_read_id(ulpi);
>>  	if (ret)
>> -		return ret;
>> +		goto err;
>>  
>>  	ret = device_register(&ulpi->dev);
>>  	if (ret)
>> -		return ret;
>> +		goto err;
> 
> I think there is another bug in the code here. Missing put_device().

So what is the correct way to create a device? Shouldn't device_register
be paired with device_unregister? And from what I can tell,
device_unregister does not put the of_node.

> If you first fix that, you should then be able to call
> fwnode_handle_put() (instead of of_node_put())

Well, we currently only have a ulpi_of_register, so I don't think we
will have a fwnode here. But I can use that if you wish.

--Sean

> from
> ulpi_dev_release(), and that should cover all cases.
> 
>>  	root = debugfs_create_dir(dev_name(dev), ULPI_ROOT);
>>  	debugfs_create_file("regs", 0444, root, ulpi, &ulpi_regs_ops);
>> @@ -314,6 +314,10 @@ static int ulpi_register(struct device *dev, struct ulpi *ulpi)
>>  		ulpi->id.vendor, ulpi->id.product);
>>  
>>  	return 0;
>> +
>> +err:
>> +	of_node_put(ulpi->dev.of_node);
>> +	return ret;
> 
> So no need for that.
> 
>>  }
>>  
>>  /**
>> @@ -357,8 +361,8 @@ void ulpi_unregister_interface(struct ulpi *ulpi)
>>  {
>>  	debugfs_remove_recursive(debugfs_lookup(dev_name(&ulpi->dev),
>>  						ULPI_ROOT));
>> -	of_node_put(ulpi->dev.of_node);
>>  	device_unregister(&ulpi->dev);
>> +	of_node_put(ulpi->dev.of_node);
>>  }
> 
> And here you can just remove that of_node_put() call.
> 
> thanks,
>