[PATCH v2 0/4] driver core: Prevent device_find_child() from modifying caller's match data

Zijun Hu
2024-08-15T14:58:22Z

This patch series is to prepare for constifying the following driver API:

struct device *device_find_child(struct device *dev, void *data,
int (*match)(struct device *dev, void *data));
to
struct device *device_find_child(struct device *dev, const void *data,
int (*match)(struct device *dev, const void *data));

How to constify the API ?
There are total 30 usages of the API in kernel tree:

For 3/30 usages, the API's match function (*match)() will modify
caller's match data @*data, and this patch series will clean up them.

For remaining 27/30, the other patch series will simply change its
relevant parameter type to const void *.

Why to constify the API ?

(1) It normally does not make sense, also does not need to, for
such device finding operation to modify caller's match data which
is mainly used for comparison.

(2) It will make the API's match function and match data parameter
have the same type as all other APIs (bus|class|driver)_find_device().

(3) It will give driver author hints about choice between this API and
the following one:
int device_for_each_child(struct device *dev, void *data,
int (*fn)(struct device *dev, void *data));

Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
---
Changes in v2:
- Give up introducing the API constify_device_find_child_helper()
- Correct commit message and inline comments
- Implement a driver specific and equivalent one instead of device_find_child()
- Link to v1: https://lore.kernel.org/r/20240811-const_dfc_prepare-v1-0-d67cc416b3d3@quicinc.com

---
Zijun Hu (4):
driver core: Make parameter check consistent for API cluster device_(for_each|find)_child()
cxl/region: Prevent device_find_child() from modifying caller's match data
firewire: core: Prevent device_find_child() from modifying caller's match data
net: qcom/emac: Prevent device_find_child() from modifying caller's match data

drivers/base/core.c | 6 ++--
drivers/cxl/core/region.c | 36 +++++++++++++++++++++++-
drivers/firewire/core-device.c | 37 +++++++++++++++++++++++--
drivers/net/ethernet/qualcomm/emac/emac-sgmii.c | 36 ++++++++++++++++++++++--
4 files changed, 107 insertions(+), 8 deletions(-)
---
base-commit: bfa54a793ba77ef696755b66f3ac4ed00c7d1248
change-id: 20240811-const_dfc_prepare-3ff23c6598e5

Best regards,
--
Zijun Hu <quic_zijuhu@quicinc.com>