[RFC PATCH v5 2/3] vfio: platform: access device property as a list of strings

[Baptiste Reynal <b.reynal@virtualopensystems.com>]

From: Antonios Motakis <a.motakis@virtualopensystems.com>

Certain device properties (e.g. the device node name, the compatible
string), are available as a list of strings (separated by the null
terminating character). Let the VFIO user query this type of properties.

Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Signed-off-by: Baptiste Reynal <b.reynal@virtualopensystems.com>

---
v4 -> v5:
 - return ENOSPC when the buffer size is too small
 - remove strlen call

v3 -> v4:
 - The list length is computed before strings copy. If the entire list
   doesn't fit, no strings are copied to the user.
---
 drivers/vfio/platform/properties.c | 43 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/platform/properties.c b/drivers/vfio/platform/properties.c
index 48c90c5..212755f 100644
--- a/drivers/vfio/platform/properties.c
+++ b/drivers/vfio/platform/properties.c
@@ -22,7 +22,48 @@ static int dev_property_get_strings(struct device *dev,
 				    char *name, unsigned *lenp,
 				    void __user *datap, unsigned long datasz)
 {
-	return -EINVAL;
+	const char **val;
+	int n, i, ret;
+
+	if (lenp == NULL)
+		return -EFAULT;
+
+	*lenp = 0;
+
+	n = device_property_read_string_array(dev, name, NULL, 0);
+	if (n < 0)
+		return n;
+
+	val = kcalloc(n, sizeof(char *), GFP_KERNEL);
+	if (!val)
+		return -ENOMEM;
+
+	ret = device_property_read_string_array(dev, name, val, n);
+	if (ret < 0)
+		goto out;
+
+	for (i = 0; i < n; i++)
+		*lenp += strlen(val[i]) + 1;
+
+	if (datasz < *lenp) {
+		ret = -ENOSPC;
+		goto out;
+	}
+
+	for (i = 0; i < n; i++) {
+		size_t len = strlen(val[i]) + 1;
+
+		if (copy_to_user(datap, val[i], len)) {
+			ret = -EFAULT;
+			goto out;
+		}
+
+		datap += len;
+	}
+
+out:
+	kfree(val);
+	return ret;
 }
 
 static int dev_property_get_uint(struct device *dev,
-- 
2.6.0