-----Original Message-----
From: Greg KH [mailto:gregkh@linuxfoundation.org]
Sent: Thursday 6 June 2019 14:29
To: Dragan Cvetic <redacted>
Cc: arnd@arndb.de; Michal Simek <redacted>; linux-arm-kernel@lists.infradead.org; robh+dt@kernel.org;
mark.rutland@arm.com; devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; Derek Kiernan [off-list ref]
Subject: Re: [PATCH V4 04/12] misc: xilinx_sdfec: Add open, close and ioctl

On Sat, May 25, 2019 at 12:37:17PM +0100, Dragan Cvetic wrote:

quoted

+static int xsdfec_dev_open(struct inode *iptr, struct file *fptr)
+{
+	return 0;
+}
+
+static int xsdfec_dev_release(struct inode *iptr, struct file *fptr)
+{
+	return 0;
+}

empty open/close functions are never needed, just drop them.

Accepted.
Will remove them.

quoted

+
+static long xsdfec_dev_ioctl(struct file *fptr, unsigned int cmd,
+			     unsigned long data)
+{
+	struct xsdfec_dev *xsdfec;
+	void __user *arg = NULL;
+	int rval = -EINVAL;
+
+	xsdfec = container_of(fptr->private_data, struct xsdfec_dev, miscdev);
+	if (!xsdfec)
+		return rval;

It is impossible for container_of() to return NULL, unless something
very magical and rare just happened.  It's just doing pointer math, you
can never check the return value of it.

Accepted.
Will remove if statement.

quoted

+
+	if (_IOC_TYPE(cmd) != XSDFEC_MAGIC)
+		return -ENOTTY;

How can this happen?

Accepted.
Will be removed.

quoted

+
+	/* check if ioctl argument is present and valid */
+	if (_IOC_DIR(cmd) != _IOC_NONE) {
+		arg = (void __user *)data;
+		if (!arg)
+			return rval;
+	}
+
+	switch (cmd) {
+	default:
+		/* Should not get here */
+		dev_warn(xsdfec->dev, "Undefined SDFEC IOCTL");

Nice that userspace has a way to fill up the kernel log :(

Just return the correct error here, don't log it.

Accepted.
Will remove log.

thanks,

greg k-h

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