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

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Message-ID: <284ed076-ac57-c90c-751d-0ced6d0c7c61@seco.com>
Date:   Tue, 25 Jan 2022 12:01:00 -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



On 1/25/22 11:53 AM, Sean Anderson wrote:
> 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.

Hm, looks like I missed the ACPI_COMPANION_SET

So this should probably be fwnode_handle_put.

But ACPI_COMPANION_SET doesn't seem to get the fwnode?

> --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,
>> 
>