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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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