Re: [linuxdc-dev]Misbehaving driver code

[Paul M. <pm...@mv...>]

On Wed, Nov 21, 2001 at 08:58:06PM +0000, Adrian McMenamin wrote:
> But rmmod produces "Device busy" error message.
>=20
This is to be expected.. as you're misusing MOD_{INC,DEC}_USE_COUNT.

> Any ideas? Is it simply because this is not a properly registered driver =
yet=20
> - or is there a coding problem?
>=20
> Any and all help etc....
>=20
[snip]

> static int __init init_aica (void)
> {
>      MOD_INC_USE_COUNT; //increment count
[snip]

This is not at all what you want to do. You're forcing its usage count up on
an initialization even though nothing is actually using it. The proper way =
to
do this would be to setup an aica_open() and stick your MOD_INC_USE_COUNT in
there, and then decrement it on an aico_close(), then hand that off to a fi=
le
operations structure when you register.

> }
>=20
> static void __exit exit_aica(void)
> {
>   /*set low bit of register to 1*/
>   printk("<1>AICA sound driver being unloaded...\n");
>   SET_AICA_REG(0x2c00) |=3D 1;
>   MOD_DEC_USE_COUNT;
>  =20
> }
>=20
Same deal here, MOD_DEC_USE_COUNT should only ever be used by a close call.
Think of the following scenario .. you bring up the device, and open()
/dev/dsp .. this should accordingly increment its usage count, as it's in u=
se
by the application that open()'ed it. Later on .. when you close() the file
descriptor, its usage count is decremented.

Checking /proc/modules will always report the current status of a module and
its usage count.. a module can't be unloaded if it's in use.

Regards,

--=20
Paul Mundt <pm...@mv...>
MontaVista Software, Inc.