[PATCH v2 3/4] firewire: core: Prevent device_find_child() from modifying caller's match data

Zijun Hu
2024-08-15T14:58:41Z

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 lookup_existing_device() 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
fw_device_find_child() instead of the old API usage.

Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
---
drivers/firewire/core-device.c | 37 +++++++++++++++++++++++++++++++++++--
1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
index 00e9a13e6c45..7fbccb113d54 100644
--- a/drivers/firewire/core-device.c
+++ b/drivers/firewire/core-device.c
@@ -33,6 +33,39 @@

#define ROOT_DIR_OFFSET 5

+struct fw_dfc_data {
+ int (*match)(struct device *dev, void *data);
+ void *data;
+ struct device *target_device;
+};
+
+static int fw_dfc_match_modify(struct device *dev, void *data)
+{
+ struct fw_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 *fw_device_find_child(struct device *parent, void *data,
+ int (*match)(struct device *dev, void *data))
+{
+ struct fw_dfc_data dfc_data = {match, data, NULL};
+
+ device_for_each_child(parent, &dfc_data, fw_dfc_match_modify);
+ return dfc_data.target_device;
+}
+
void fw_csr_iterator_init(struct fw_csr_iterator *ci, const u32 *p)
{
ci->p = p + 1;
@@ -1087,8 +1120,8 @@ static void fw_device_init(struct work_struct *work)
return;
}

- revived_dev = device_find_child(card->device,
- device, lookup_existing_device);
+ revived_dev = fw_device_find_child(card->device, device,
+ lookup_existing_device);
if (revived_dev) {
put_device(revived_dev);
fw_device_release(&device->device);

--
2.34.1