On 02/07/2020 00:04, Leonardo Bras wrote:

On Wed, 2020-07-01 at 18:17 +1000, Alexey Kardashevskiy wrote:

quoted

quoted

+#define DDW_EXT_SIZE		0
+#define DDW_EXT_RESET_DMA_WIN	1
+#define DDW_EXT_QUERY_OUT_SIZE	2

#define DDW_EXT_LAST (DDW_EXT_QUERY_OUT_SIZE + 1)
...

quoted

+
 static struct iommu_table_group *iommu_pseries_alloc_group(int node)
 {
 	struct iommu_table_group *table_group;

@@ -339,7 +343,7 @@ struct direct_window {
 /* Dynamic DMA Window support */
 struct ddw_query_response {
 	u32 windows_available;
-	u32 largest_available_block;
+	u64 largest_available_block;
 	u32 page_size;
 	u32 migration_capable;
 };

@@ -875,13 +879,29 @@ static int find_existing_ddw_windows(void)
 machine_arch_initcall(pseries, find_existing_ddw_windows);
 
 static int query_ddw(struct pci_dev *dev, const u32 *ddw_avail,
-			struct ddw_query_response *query)
+		     struct ddw_query_response *query,
+		     struct device_node *parent)
 {
 	struct device_node *dn;
 	struct pci_dn *pdn;
-	u32 cfg_addr;
+	u32 cfg_addr, query_out[5], ddw_ext[DDW_EXT_QUERY_OUT_SIZE + 1];

... and use DDW_EXT_LAST here.

Because of the growing nature of ddw-extensions, I intentionally let
this be (DDW_EXT_QUERY_OUT_SIZE + 1). If we create a DDW_EXT_LAST, it
will be incremented in the future if more extensions come to exist.

I mean, I previously saw no reason for allocating space for extensions
after the desired one, as they won't be used here.

Ah, my bad, you're right.

quoted

quoted

 	u64 buid;
-	int ret;
+	int ret, out_sz;
+
+	/*
+	 * From LoPAR level 2.8, "ibm,ddw-extensions" index 3 can rule how many
+	 * output parameters ibm,query-pe-dma-windows will have, ranging from
+	 * 5 to 6.
+	 */
+
+	ret = of_property_read_u32_array(parent, "ibm,ddw-extensions",
+					 &ddw_ext[0],
+					 DDW_EXT_QUERY_OUT_SIZE + 1);

In this case, I made sure not to cross (DDW_EXT_QUERY_OUT_SIZE + 1)
while reading the extensions from the property.

What do you think about it? 

I think you want something like:

static inline int ddw_read_ext(const struct device_node *np, int extnum,
u32 *ret)
{
retun of_property_read_u32_index(np, "ibm,ddw-extensions", extnum + 1, ret);
}

These "+1"'s all over the place are confusing.


-- 
Alexey