PCI: Force trailing new line to resource_alignment_param in sysfs

When 'pci=resource_alignment=' is specified on the command line, there is
no trailing new line.  Then, when it's read through the corresponding sysfs
attribute, there will be no newline and a cat command will not show
correctly in a shell. If the parameter is set through sysfs a new line will
be stored and it will 'cat' correctly.

To solve this, append a new line character in the show function if one does
not already exist.

Link: https://lore.kernel.org/r/20190822161013.5481-4-logang@deltatee.comSigned-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci.c

@@ -6126,6 +6126,16 @@ static ssize_t resource_alignment_show(struct bus_type *bus, char *buf)
 		count = snprintf(buf, PAGE_SIZE, "%s", resource_alignment_param);
 	spin_unlock(&resource_alignment_lock);
 
+	/*
+	 * When set by the command line, resource_alignment_param will not
+	 * have a trailing line feed, which is ugly. So conditionally add
+	 * it here.
+	 */
+	if (count >= 2 && buf[count - 2] != '\n' && count < PAGE_SIZE - 1) {
+		buf[count - 1] = '\n';
+		buf[count++] = 0;
+	}
+
 	return count;
 }