libertas: if_spi, driver for libertas GSPI devices

Add initial support for libertas devices using a GSPI interface.  This has
been tested with the 8686.

GSPI is intended to be used on embedded systems. Board-specific parameters are
required (see libertas_spi.h).

Thanks to everyone who took a look at the earlier versions of the patch.

Signed-off-by: Colin McCabe <colin@cozybit.com>
Signed-off-by: Andrey Yurovsky <andrey@cozybit.com>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/linux/spi/libertas_spi.h

@@ -0,0 +1,25 @@
+/*
+ * board-specific data for the libertas_spi driver.
+ *
+ * Copyright 2008 Analog Devices Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ */
+#ifndef _LIBERTAS_SPI_H_
+#define _LIBERTAS_SPI_H_
+struct libertas_spi_platform_data {
+	/* There are two ways to read data from the WLAN module's SPI
+	 * interface. Setting 0 or 1 here controls which one is used.
+	 *
+	 * Usually you want to set use_dummy_writes = 1.
+	 * However, if that doesn't work or if you are using a slow SPI clock
+	 * speed, you may want to use 0 here. */
+	u16 use_dummy_writes;
+
+	/* GPIO number to use as chip select */
+	u16 gpio_cs;
+};
+#endif