[ 20/75] serial: 8250: Keep 8250.<xxxx> module options functional after driver rename

[Greg Kroah-Hartman]

3.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Josh Boyer <jwboyer@xxxxxxxxxx>

commit f2b8dfd9e480c3db3bad0c25c590a5d11b31f4ef upstream.

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@xxxxxxxxxx>
Acked-by: Jiri Slaby <jslaby@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/tty/serial/8250/8250.c |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

--- a/drivers/tty/serial/8250/8250.c
+++ b/drivers/tty/serial/8250/8250.c
@@ -3430,3 +3430,32 @@ module_param_array(probe_rsa, ulong, &pr
 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


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