[PATCH] parport: check exclusive access before register

[PATCH] parport: check exclusive access before register

[Sudip Mukherjee]

As of now we were starting the registration process and after the device
is registered we were checking if the device can be used by the
parport. Now lets check it first so that we do not need to go through
the registration process only to fail at the end.
The original exclusive access check at the end is still there so that we
do not get any surprises if two different process registers its device
with same parport and with exclusive access at the same time.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
---

Hi Greg,
One doubt - if anyone sends any patch regarding parport, it will be
addressed to me. so do i need to forward it to you?

 drivers/parport/share.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/parport/share.c b/drivers/parport/share.c
index 697c6d7..8067f54 100644
--- a/drivers/parport/share.c
+++ b/drivers/parport/share.c
@@ -708,6 +708,20 @@ parport_register_device(struct parport *port, const char *name,
 		}
 	}
 
+	if (flags & PARPORT_DEV_EXCL) {
+		if (port->physport->devices) {
+			/*
+			 * If a device is already registered and this new
+			 * device wants exclusive access, then no need to
+			 * continue as we can not grant exclusive access to
+			 * this device.
+			 */
+			pr_err("%s: cannot grant exclusive access for device %s\n",
+			       port->name, name);
+			return NULL;
+		}
+	}
+
 	/* We up our own module reference count, and that of the port
            on which a device is to be registered, to ensure that
            neither of us gets unloaded while we sleep in (e.g.)
@@ -827,6 +841,20 @@ parport_register_dev_model(struct parport *port, const char *name,
 		}
 	}
 
+	if (par_dev_cb->flags & PARPORT_DEV_EXCL) {
+		if (port->physport->devices) {
+			/*
+			 * If a device is already registered and this new
+			 * device wants exclusive access, then no need to
+			 * continue as we can not grant exclusive access to
+			 * this device.
+			 */
+			pr_err("%s: cannot grant exclusive access for device %s\n",
+			       port->name, name);
+			return NULL;
+		}
+	}
+
 	if (!try_module_get(port->ops->owner))
 		return NULL;
 
-- 
1.8.1.2

Re: [PATCH] parport: check exclusive access before register

[Greg KH]

On Fri, Jun 12, 2015 at 03:20:20PM +0530, Sudip Mukherjee wrote:
> As of now we were starting the registration process and after the device
> is registered we were checking if the device can be used by the
> parport. Now lets check it first so that we do not need to go through
> the registration process only to fail at the end.
> The original exclusive access check at the end is still there so that we
> do not get any surprises if two different process registers its device
> with same parport and with exclusive access at the same time.
> 
> Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
> ---
> 
> Hi Greg,
> One doubt - if anyone sends any patch regarding parport, it will be
> addressed to me. so do i need to forward it to you?

Yes, please do so, I'll be glad to queue them up in my trees to go to
Linus.

thanks,

greg k-h