linux-kernel - Re: [PATCH v4 2/2] net: qcom/emac: Find sgmii_ops by device_for_each

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Message-ID: <58106753-389a-42a1-88df-0cf006b2faac@quicinc.com>
Date: Thu, 5 Sep 2024 17:09:43 +0800
From: quic_zijuhu <quic_zijuhu@...cinc.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Zijun Hu
	<zijun_hu@...oud.com>
CC: Davidlohr Bueso <dave@...olabs.net>,
        Jonathan Cameron
	<jonathan.cameron@...wei.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alison
 Schofield <alison.schofield@...el.com>,
        Vishal Verma
	<vishal.l.verma@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Dan Williams
	<dan.j.williams@...el.com>,
        Timur Tabi <timur@...nel.org>,
        "David S. Miller"
	<davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, <linux-cxl@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] net: qcom/emac: Find sgmii_ops by
 device_for_each_child()

On 9/5/2024 1:33 PM, Greg Kroah-Hartman wrote:
> On Thu, Sep 05, 2024 at 07:29:10AM +0200, Greg Kroah-Hartman wrote:
>> On Thu, Sep 05, 2024 at 08:36:10AM +0800, Zijun Hu wrote:
>>> From: Zijun Hu <quic_zijuhu@...cinc.com>
>>>
>>> To prepare for constifying the following old driver core API:
>>>
>>> struct device *device_find_child(struct device *dev, void *data,
>>> 		int (*match)(struct device *dev, void *data));
>>> to new:
>>> struct device *device_find_child(struct device *dev, const void *data,
>>> 		int (*match)(struct device *dev, const void *data));
>>>
>>> The new API does not allow its match function (*match)() to modify
>>> caller's match data @*data, but emac_sgmii_acpi_match() as the old
>>> API's match function indeed modifies relevant match data, so it is not
>>> suitable for the new API any more, solved by using device_for_each_child()
>>> to implement relevant finding sgmii_ops function.
>>>
>>> By the way, this commit does not change any existing logic.
>>>
>>> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
>>> ---
>>>  drivers/net/ethernet/qualcomm/emac/emac-sgmii.c | 22 +++++++++++++++++-----
>>>  1 file changed, 17 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c b/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c
>>> index e4bc18009d08..29392c63d115 100644
>>> --- a/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c
>>> +++ b/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c
>>> @@ -293,6 +293,11 @@ static struct sgmii_ops qdf2400_ops = {
>>>  };
>>>  #endif
>>>  
>>> +struct emac_match_data {
>>> +	struct sgmii_ops **sgmii_ops;
>>> +	struct device *target_device;
>>> +};
>>> +
>>>  static int emac_sgmii_acpi_match(struct device *dev, void *data)
>>>  {
>>>  #ifdef CONFIG_ACPI
>>> @@ -303,7 +308,7 @@ static int emac_sgmii_acpi_match(struct device *dev, void *data)
>>>  		{}
>>>  	};
>>>  	const struct acpi_device_id *id = acpi_match_device(match_table, dev);
>>> -	struct sgmii_ops **ops = data;
>>> +	struct emac_match_data *match_data = data;
>>>  
>>>  	if (id) {
>>>  		acpi_handle handle = ACPI_HANDLE(dev);
>>> @@ -324,10 +329,12 @@ static int emac_sgmii_acpi_match(struct device *dev, void *data)
>>>  
>>>  		switch (hrv) {
>>>  		case 1:
>>> -			*ops = &qdf2432_ops;
>>> +			*match_data->sgmii_ops = &qdf2432_ops;
>>> +			match_data->target_device = get_device(dev);
>>>  			return 1;
>>>  		case 2:
>>> -			*ops = &qdf2400_ops;
>>> +			*match_data->sgmii_ops = &qdf2400_ops;
>>> +			match_data->target_device = get_device(dev);
>>
>> Where is put_device() now called?
> 
> Nevermind, I see it now.
> 
> That being said, this feels wrong still, why not just do this "set up
> the ops" logic _after_ you find the device and not here in the match
> function?
> 

that will become more complex since

1) it need to change match_data->sgmii_ops type from struct sgmii_ops **
to struct sgmii_ops * which is not same as type of original @data

2) it also needs to implement a extra finding function find_xyz()
similar as cxl/region find_free_decoder()

3) it need to extra condition assignment after find aim device.


actually, this scenario is a bit different with cxl/region as shown below:
for cxl/region, we only need to get aim device
for this scenario, we need to get both aim device and relevant sgmii_ops

> thanks,
> 
> greg k-h