rapidio/tsi721: add messaging mbox selector parameter

Add module parameter to allow load time configuration of available
RapidIO messaging mailboxes (MBOX1 - MBOX4).

Having a messaging MBOX selector mask allows to define which MBOXes are
controlled by the mport device driver and reserve some of them for
direct use by other drivers.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Bounine <[e-mail]>
Tested-by: Barry Wood <[e-mail]>
Cc: Matt Porter <[e-mail]>
Cc: Andre van Herk <[e-mail]>
Cc: Barry Wood <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/rapidio/tsi721.txt

···
         0 = 128B, 1 = 256B, 2 = 512B, 3 = 1024B, 4 = 2048B and 5 = 4096B.
         Default value is '-1' (= keep platform setting).
 
+- 'mbox_sel' - RIO messaging MBOX selection mask. This is a bitmask that defines
+        messaging MBOXes are managed by this device driver. Mask bits 0 - 3
+        correspond to MBOX0 - MBOX3. MBOX is under driver's control if the
+        corresponding bit is set to '1'. Default value is 0x0f (= all).
+
 II. Known problems
 
   None.

drivers/rapidio/devices/tsi721.c

···
 module_param(pcie_mrrs, int, S_IRUGO);
 MODULE_PARM_DESC(pcie_mrrs, "PCIe MRRS override value (0...5)");
 
+static u8 mbox_sel = 0x0f;
+module_param(mbox_sel, byte, S_IRUGO);
+MODULE_PARM_DESC(mbox_sel,
+		 "RIO Messaging MBOX Selection Mask (default: 0x0f = all)");
+
 static void tsi721_omsg_handler(struct tsi721_device *priv, int ch);
 static void tsi721_imsg_handler(struct tsi721_device *priv, int ch);
 
···
 		goto out;
 	}
 
+	if ((mbox_sel & (1 << mbox)) == 0) {
+		rc = -ENODEV;
+		goto out;
+	}
+
 	priv->omsg_ring[mbox].dev_id = dev_id;
 	priv->omsg_ring[mbox].size = entries;
 	priv->omsg_ring[mbox].sts_rdptr = 0;
···
 	    (entries > TSI721_IMSGD_RING_SIZE) ||
 	    (!is_power_of_2(entries)) || mbox >= RIO_MAX_MBOX) {
 		rc = -EINVAL;
+		goto out;
+	}
+
+	if ((mbox_sel & (1 << mbox)) == 0) {
+		rc = -ENODEV;
 		goto out;
 	}