i3c: Add stub functions when I3C support is disabled

When I3C is disabled, unused functions are removed by the linker because
the driver relies on regmap and no I3C devices are registered, so normal
I3C paths are never called.

However, some drivers may still call low-level I3C transfer helpers.
Provide stub implementations to avoid adding conditional ifdefs everywhere.

Add stubs for i3c_device_do_xfers() and
i3c_device_get_supported_xfer_mode() only. Other stubs will be introduced
when they are actually needed.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512230418.nu3V6Yua-lkp@intel.com/
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20251230145718.4088694-1-Frank.Li@nxp.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/include/linux/i3c/device.h b/include/linux/i3c/device.h
index 39a1ff18087110311f9178b0bf2dc7c730133c5b..971d53349b6f604aa5d84febf63062d597b1d7b4 100644 (file)
--- a/include/linux/i3c/device.h
+++ b/include/linux/i3c/device.h
@@ -305,8 +305,23 @@ static __always_inline void i3c_i2c_driver_unregister(struct i3c_driver *i3cdrv,
                      i3c_i2c_driver_unregister,        \
                      __i2cdrv)
 
+#if IS_ENABLED(CONFIG_I3C)
 int i3c_device_do_xfers(struct i3c_device *dev, struct i3c_xfer *xfers,
                        int nxfers, enum i3c_xfer_mode mode);
+u32 i3c_device_get_supported_xfer_mode(struct i3c_device *dev);
+#else
+static inline int
+i3c_device_do_xfers(struct i3c_device *dev, struct i3c_xfer *xfers,
+                   int nxfers, enum i3c_xfer_mode mode)
+{
+       return -EOPNOTSUPP;
+}
+
+static inline u32 i3c_device_get_supported_xfer_mode(struct i3c_device *dev)
+{
+       return 0;
+}
+#endif
 
 int i3c_device_do_setdasa(struct i3c_device *dev);
 
@@ -348,6 +363,5 @@ int i3c_device_request_ibi(struct i3c_device *dev,
 void i3c_device_free_ibi(struct i3c_device *dev);
 int i3c_device_enable_ibi(struct i3c_device *dev);
 int i3c_device_disable_ibi(struct i3c_device *dev);
-u32 i3c_device_get_supported_xfer_mode(struct i3c_device *dev);
 
 #endif /* I3C_DEV_H */