linux-kernel - [PATCH 3/5] char: lp: use first unused lp number while registering

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Date:   Fri,  7 Dec 2018 14:27:32 +0000
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>
Cc:     linux-kernel@...r.kernel.org,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: [PATCH 3/5] char: lp: use first unused lp number while registering

When the parallel port is usb based and the lp attaches to it based on
LP_PARPORT_AUTO, we do get /dev/lp0 and when we remove the usb device
/dev/lp0 is unregistered. But if we now reconnect the usb device we get
/dev/lp1, another disconnection and reconnection and we get /dev/lp2.

Use the port number array to find the first unused lp number and use
that to register the lp device with the parallel port.

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
---
 drivers/char/lp.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/char/lp.c b/drivers/char/lp.c
index e21ed4007d0f..0e081f521f51 100644
--- a/drivers/char/lp.c
+++ b/drivers/char/lp.c
@@ -958,7 +958,11 @@ static void lp_attach(struct parport *port)
 			printk(KERN_INFO "lp: ignoring parallel port (max. %d)\n",LP_NO);
 			return;
 		}
-		if (!lp_register(lp_count, port))
+		for (i = 0; i < LP_NO; i++)
+			if (port_num[i] == -1)
+				break;
+
+		if (!lp_register(i, port))
 			lp_count++;
 		break;
 
-- 
2.11.0