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

From: quic_zijuhu
Date: Thu Sep 05 2024 - 04:31:10 EST


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@xxxxxxxxxxx>
>>
>> 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@xxxxxxxxxxx>
>> ---
>> 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