Hi,

I'm working on a driver for I2C-Tiny-USB[1], a USB device (Atmel/AVR or
RP2040/Pico) providing an i2c bus to the system, similar to the Silicon Labs
CP2112 (my next driver on the list). As this is a USB device, it must be
able to be attached and detached, and it must also detach its child iic
device.

But the iic driver doesn't implement iic_detach() and so config_detach()
in my driver panics the kernel with the message: "forced detach of iic1
failed". So I added a few lines to i2c.c. What do you think?

[1] https://github.com/harbaum/I2C-Tiny-USB

diff --git sys/dev/i2c/i2c.c sys/dev/i2c/i2c.c
index 0d63b40d136..5b0d9609530 100644
--- sys/dev/i2c/i2c.c
+++ sys/dev/i2c/i2c.c
@@ -54,12 +54,14 @@ struct iic_softc {
 
 int	iic_match(struct device *, void *, void *);
 void	iic_attach(struct device *, struct device *, void *);
+int	iic_detach(struct device *, int);
 int	iic_search(struct device *, void *, void *);
 
 const struct cfattach iic_ca = {
 	sizeof (struct iic_softc),
 	iic_match,
-	iic_attach
+	iic_attach,
+	iic_detach
 };
 
 struct cfdriver iic_cd = {
@@ -144,6 +146,12 @@ iic_attach(struct device *parent, struct device *self, void *aux)
 		iic_scan(self, aux);
 }
 
+int
+iic_detach(struct device *self, int flags)
+{
+	return (config_detach_children(self, flags));
+}
+
 int
 iic_is_compatible(const struct i2c_attach_args *ia, const char *name)
 {

-- 
Denis