[v4] driver core: Prevent device_find_child() from modifying caller's match data

[PATCH v4 2/2] net: qcom/emac: Find sgmii_ops by device_for_each_child()

Posted by Zijun Hu 1 year, 3 months ago

From: Zijun Hu <quic_zijuhu@quicinc.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@quicinc.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);
 			return 1;
 		}
 	}
@@ -356,10 +363,15 @@ int emac_sgmii_config(struct platform_device *pdev, struct emac_adapter *adpt)
 	int ret;
 
 	if (has_acpi_companion(&pdev->dev)) {
+		struct emac_match_data match_data = {
+			.sgmii_ops = &phy->sgmii_ops,
+			.target_device = NULL,
+		};
 		struct device *dev;
 
-		dev = device_find_child(&pdev->dev, &phy->sgmii_ops,
-					emac_sgmii_acpi_match);
+		device_for_each_child(&pdev->dev, &match_data, emac_sgmii_acpi_match);
+		/* Need to put_device(@dev) after use */
+		dev = match_data.target_device;
 
 		if (!dev) {
 			dev_warn(&pdev->dev, "cannot find internal phy node\n");

-- 
2.34.1

Re: [PATCH v4 2/2] net: qcom/emac: Find sgmii_ops by device_for_each_child()

Posted by Greg Kroah-Hartman 1 year, 3 months ago

On Thu, Sep 05, 2024 at 08:36:10AM +0800, Zijun Hu wrote:
> From: Zijun Hu <quic_zijuhu@quicinc.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@quicinc.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?

>  			return 1;
>  		}
>  	}
> @@ -356,10 +363,15 @@ int emac_sgmii_config(struct platform_device *pdev, struct emac_adapter *adpt)
>  	int ret;
>  
>  	if (has_acpi_companion(&pdev->dev)) {
> +		struct emac_match_data match_data = {
> +			.sgmii_ops = &phy->sgmii_ops,
> +			.target_device = NULL,
> +		};
>  		struct device *dev;
>  
> -		dev = device_find_child(&pdev->dev, &phy->sgmii_ops,
> -					emac_sgmii_acpi_match);
> +		device_for_each_child(&pdev->dev, &match_data, emac_sgmii_acpi_match);
> +		/* Need to put_device(@dev) after use */
> +		dev = match_data.target_device;


Why this new comment?  That's always required and happens down below in
the function, right?  Otherwise, what changed?

thanks,

greg k-h

Re: [PATCH v4 2/2] net: qcom/emac: Find sgmii_ops by device_for_each_child()

Posted by quic_zijuhu 1 year, 3 months ago

On 9/5/2024 1:29 PM, Greg Kroah-Hartman wrote:
> On Thu, Sep 05, 2024 at 08:36:10AM +0800, Zijun Hu wrote:
>> From: Zijun Hu <quic_zijuhu@quicinc.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@quicinc.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?
> 
>>  			return 1;
>>  		}
>>  	}
>> @@ -356,10 +363,15 @@ int emac_sgmii_config(struct platform_device *pdev, struct emac_adapter *adpt)
>>  	int ret;
>>  
>>  	if (has_acpi_companion(&pdev->dev)) {
>> +		struct emac_match_data match_data = {
>> +			.sgmii_ops = &phy->sgmii_ops,
>> +			.target_device = NULL,
>> +		};
>>  		struct device *dev;
>>  
>> -		dev = device_find_child(&pdev->dev, &phy->sgmii_ops,
>> -					emac_sgmii_acpi_match);
>> +		device_for_each_child(&pdev->dev, &match_data, emac_sgmii_acpi_match);
>> +		/* Need to put_device(@dev) after use */
>> +		dev = match_data.target_device;
> 
> 
> Why this new comment?  That's always required and happens down below in
> the function, right?  Otherwise, what changed?
> 

device_find_child() will get_device() by itself and that is obvious.

device_for_each_child() will not get_device() by itself, we get_device()
in its function parameter to make it equivalent with device_find_child()
this get_device() is not obvious, so add the inline comments to prompt
user put_device after use.

yes, and the relevant put_device() don't happen immediately.

> thanks,
> 
> greg k-h

Re: [PATCH v4 2/2] net: qcom/emac: Find sgmii_ops by device_for_each_child()

Posted by Greg Kroah-Hartman 1 year, 3 months ago

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@quicinc.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@quicinc.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?

thanks,

greg k-h

Re: [PATCH v4 2/2] net: qcom/emac: Find sgmii_ops by device_for_each_child()

Posted by Zijun Hu 1 year, 3 months ago

On 2024/9/5 13:33, 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@quicinc.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@quicinc.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?
> 
sorry, let me complement a little reply to last one.

This change will use emac_sgmii_acpi_match() as device_for_each_child()
function parameter, so may not regard emac_sgmii_acpi_match() as
match() function anymore.

> thanks,
> 
> greg k-h

Re: [PATCH v4 2/2] net: qcom/emac: Find sgmii_ops by device_for_each_child()

Posted by quic_zijuhu 1 year, 3 months ago

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@quicinc.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@quicinc.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