linux-kernel - Re: [PATCH v2] net: ethernet: support "fixed-link" DT key/node on nb8800 driver

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Date:	Fri, 05 Feb 2016 14:13:59 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Sebastian Frias <sf84@...oste.net>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, mason <slash.tmp@...e.fr>
Subject: Re: [PATCH v2] net: ethernet: support "fixed-link" DT key/node on nb8800 driver

Sebastian Frias <sf84@...oste.net> writes:

> On 02/05/2016 02:58 PM, Måns Rullgård wrote:
>> Sebastian Frias <sf84@...oste.net> writes:
>>
>>> Signed-off-by: Sebastian Frias <sf84@...oste.net>
>>> ---
>>>   drivers/net/ethernet/aurora/nb8800.c | 15 ++++++++++++---
>>>   1 file changed, 12 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/aurora/nb8800.c
>>> b/drivers/net/ethernet/aurora/nb8800.c
>>> index ecc4a33..dd7bedc 100644
>>> --- a/drivers/net/ethernet/aurora/nb8800.c
>>> +++ b/drivers/net/ethernet/aurora/nb8800.c
>>> @@ -1462,9 +1462,18 @@ static int nb8800_probe(struct platform_device *pdev)
>>>
>>>   	priv->phy_node = of_parse_phandle(pdev->dev.of_node, "phy-handle", 0);
>>>   	if (!priv->phy_node) {
>>> -		dev_err(&pdev->dev, "no PHY specified\n");
>>> -		ret = -ENODEV;
>>> -		goto err_free_bus;
>>> +		if (of_phy_is_fixed_link(pdev->dev.of_node)) {
>>> +			ret = of_phy_register_fixed_link(pdev->dev.of_node);
>>> +			if (ret < 0) {
>>> +				dev_err(&pdev->dev, "bad fixed-link spec\n");
>>> +				goto err_free_bus;
>>> +			}
>>> +			priv->phy_node = of_node_get(pdev->dev.of_node);
>>> +		} else {
>>> +			dev_err(&pdev->dev, "no PHY specified\n");
>>> +			ret = -ENODEV;
>>> +			goto err_free_bus;
>>> +		}
>>>   	}
>>
>> Maybe it would be clearer to reduce the if() nesting a bit, like this
>> for instance:
>>
>> 	if (of_phy_is_fixed_link(pdev->dev.of_node)) {
>> 		ret = of_phy_register_fixed_link(pdev->dev.of_node);
>> 		if (ret < 0) {
>> 			dev_err(&pdev->dev, "bad fixed-link spec\n");
>> 			goto err_free_bus;
>> 		}
>> 		priv->phy_node = of_node_get(pdev->dev.of_node);
>> 	}
>>
>> 	if (!priv->phy_node)
>> 		priv->phy_node = of_parse_phandle(pdev->dev.of_node,
>> 						  "phy-handle", 0);
>>
>> 	if (!priv->phy_node) {
>> 		dev_err(&pdev->dev, "no PHY specified\n");
>> 		ret = -ENODEV;
>> 		goto err_free_bus;
>> 	}
>>
>>
>
> Thanks Måns for your comments.
> With old code + my patch, we only hit 1 comparison in the general
> case, and a 2nd one in "fixed-link" case.
> With your suggestion above, it would mean that we hit 3 comparisons
> all the time.
> If you are ok with the 3 comparisons, I can post a v3.

This is code that runs once so IMO clarity is more important than a
minuscule speed difference.

-- 
Måns Rullgård