Re: [PATCH v2] serial: 8250: Keep 8250. module options functional after driver rename

Jiri Slaby
2013-03-10T22:33:30Z

On 03/10/2013 03:33 PM, Josh Boyer wrote:
> With commit 835d844d1 (8250_pnp: do pnp probe before legacy probe), the
> 8250 driver was renamed to 8250_core. This means any existing usage of
> the 8259.<xxxx> module parameters or as a kernel command line switch is
> now broken, as the 8250_core driver doesn't parse options belonging to
> something called "8250".
>
> To solve this, we redefine the module options in a dummy function using
> a redefined MODULE_PARAM_PREFX when built into the kernel. In the case
> where we're building as a module, we provide an alias to the old 8250
> name. The dummy function prevents compiler errors due to global variable
> redefinitions that happen as part of the module_param_ macro expansions.
>
> Signed-off-by: Josh Boyer <jwboyer@redhat.com>

Despite the inevitable ugly nature of the approach:

Acked-by: Jiri Slaby <jslaby@suse.cz>

> ---
> v2: Use __module_param_call for probe_rsa instead of undefining the
> __param_check macro as suggested by Jiri Slaby
>
> drivers/tty/serial/8250/8250.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c
> index 0efc815..f982633 100644
> --- a/drivers/tty/serial/8250/8250.c
> +++ b/drivers/tty/serial/8250/8250.c
> @@ -3396,3 +3396,32 @@ module_param_array(probe_rsa, ulong, &probe_rsa_count, 0444);
> MODULE_PARM_DESC(probe_rsa, "Probe I/O ports for RSA");
> #endif
> MODULE_ALIAS_CHARDEV_MAJOR(TTY_MAJOR);
> +
> +#ifndef MODULE
> +/* This module was renamed to 8250_core in 3.7. Keep the old "8250" name
> + * working as well for the module options so we don't break people. We
> + * need to keep the names identical and the convenient macros will happily
> + * refuse to let us do that by failing the build with redefinition errors
> + * of global variables. So we stick them inside a dummy function to avoid
> + * those conflicts. The options still get parsed, and the redefined
> + * MODULE_PARAM_PREFIX lets us keep the "8250." syntax alive.
> + *
> + * This is hacky. I'm sorry.
> + */
> +static void __used s8250_options(void)
> +{
> +#undef MODULE_PARAM_PREFIX
> +#define MODULE_PARAM_PREFIX "8250."
> +
> + module_param_cb(share_irqs, &param_ops_uint, &share_irqs, 0644);
> + module_param_cb(nr_uarts, &param_ops_uint, &nr_uarts, 0644);
> + module_param_cb(skip_txen_test, &param_ops_uint, &skip_txen_test, 0644);
> +#ifdef CONFIG_SERIAL_8250_RSA
> + __module_param_call(MODULE_PARAM_PREFIX, probe_rsa,
> + &param_array_ops, .arr = &__param_arr_probe_rsa,
> + 0444, -1);
> +#endif
> +}
> +#else
> +MODULE_ALIAS("8250");
> +#endif
>

--
js
suse labs