linux-kernel - [PATCH] ppdev: check before attaching port

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Message-Id: <1478985732-4557-1-git-send-email-sudipm.mukherjee@gmail.com>
Date:   Sat, 12 Nov 2016 21:22:12 +0000
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: [PATCH] ppdev: check before attaching port

After parport starts using the device model, all pardevice drivers
should decide in their match_port callback function if they want to
attach with that particulatr port. ppdev has been converted to use the
new parport device-model code but pp_attach() tried to attach with all
the ports.
Create a new array of pointer and use that to remember the ports we
have attached. And use that information to skip attaching ports which
we have already attached.

Tested-by: Joe Lawrence <joe.lawrence@...hat.com>
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
---
 drivers/char/ppdev.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
index 6af1ce0..b30d68c 100644
--- a/drivers/char/ppdev.c
+++ b/drivers/char/ppdev.c
@@ -86,6 +86,9 @@ struct pp_struct {
 	long default_inactivity;
 };
 
+/* should we use PARDEVICE_MAX here? */
+static struct device *devices[PARPORT_MAX];
+
 /* pp_struct.flags bitfields */
 #define PP_CLAIMED    (1<<0)
 #define PP_EXCL       (1<<1)
@@ -789,13 +792,29 @@ static unsigned int pp_poll(struct file *file, poll_table *wait)
 
 static void pp_attach(struct parport *port)
 {
-	device_create(ppdev_class, port->dev, MKDEV(PP_MAJOR, port->number),
-		      NULL, "parport%d", port->number);
+	struct device *ret;
+
+	if (devices[port->number])
+		return;
+
+	ret = device_create(ppdev_class, port->dev,
+			    MKDEV(PP_MAJOR, port->number), NULL,
+			    "parport%d", port->number);
+	if (IS_ERR(ret)) {
+		pr_err("Failed to create device parport%d\n",
+		       port->number);
+		return;
+	}
+	devices[port->number] = ret;
 }
 
 static void pp_detach(struct parport *port)
 {
+	if (!devices[port->number])
+		return;
+
 	device_destroy(ppdev_class, MKDEV(PP_MAJOR, port->number));
+	devices[port->number] = NULL;
 }
 
 static int pp_probe(struct pardevice *par_dev)
-- 
1.9.1