[PATCH v2 4/4] net: qcom/emac: Prevent device_find_child() from modifying caller's match data

Zijun Hu
2024-08-15T14:58:48Z

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, fixed by implementing a equivalent
emac_device_find_child() instead of the old API usage.

Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
---
drivers/net/ethernet/qualcomm/emac/emac-sgmii.c | 36 +++++++++++++++++++++++--
1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c b/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c
index e4bc18009d08..1c799be77d99 100644
--- a/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c
+++ b/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c
@@ -47,6 +47,38 @@

#define SERDES_START_WAIT_TIMES 100

+struct emac_dfc_data {
+ int (*match)(struct device *dev, void *data);
+ void *data;
+ struct device *target_device;
+};
+
+static int emac_dfc_match_modify(struct device *dev, void *data)
+{
+ struct emac_dfc_data *dfc_data = data;
+ int res;
+
+ res = dfc_data->match(dev, dfc_data->data);
+ if (res && get_device(dev)) {
+ dfc_data->target_device = dev;
+ return res;
+ }
+
+ return 0;
+}
+
+/* I have the same function as device_find_child() but allow to modify
+ * caller's match data @*data.
+ */
+static struct device *emac_device_find_child(struct device *parent, void *data,
+ int (*match)(struct device *dev, void *data))
+{
+ struct emac_dfc_data dfc_data = {match, data, NULL};
+
+ device_for_each_child(parent, &dfc_data, emac_dfc_match_modify);
+ return dfc_data.target_device;
+}
+
int emac_sgmii_init(struct emac_adapter *adpt)
{
if (!(adpt->phy.sgmii_ops && adpt->phy.sgmii_ops->init))
@@ -358,8 +390,8 @@ int emac_sgmii_config(struct platform_device *pdev, struct emac_adapter *adpt)
if (has_acpi_companion(&pdev->dev)) {
struct device *dev;

- dev = device_find_child(&pdev->dev, &phy->sgmii_ops,
- emac_sgmii_acpi_match);
+ dev = emac_device_find_child(&pdev->dev, &phy->sgmii_ops,
+ emac_sgmii_acpi_match);

if (!dev) {
dev_warn(&pdev->dev, "cannot find internal phy node\n");

--
2.34.1