[PATCH 3/5] block/prl-xml: add bdrv_probe

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

From: Klim Kireev <klim.kireev@virtuozzo.com>

This commit adds bdrv_probe implementation.
It checks the filename (it must be DiskDescriptor.xml).
Then it checks correctness of the xml file using libxml2.

Signed-off-by: Klim Kireev <klim.kireev@virtuozzo.com>
---
 block/prl-xml.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/block/prl-xml.c b/block/prl-xml.c
index 5ab32bb6ab..023651342c 100644
--- a/block/prl-xml.c
+++ b/block/prl-xml.c
@@ -467,6 +467,30 @@ fail:
     return ret;
 }
 
+static int prl_probe_xml(const uint8_t *data, int buf_size,
+                         const char *filename)
+{
+    xmlDoc *doc = NULL;
+    xmlNodePtr root;
+
+    if (strcmp(basename(filename), PRL_XML_FILENAME) != 0) {
+        return 0;
+    }
+
+    doc = xmlReadFile(filename, NULL, XML_PARSE_NOERROR | XML_PARSE_NOWARNING);
+    if (doc == NULL) {
+        return 0;
+    }
+
+    root = xmlDocGetRootElement(doc);
+    if (root == NULL) {
+        return 0;
+    }
+
+    xmlFreeDoc(doc);
+    return 100;
+}
+
 static coroutine_fn int
 prl_co_readv(BlockDriverState *bs, int64_t sector_num,
              int nb_sectors, QEMUIOVector *qiov)
@@ -499,6 +523,7 @@ static coroutine_fn int prl_co_flush_to_os(BlockDriverState *bs)
 static BlockDriver bdrv_prl_xml = {
     .format_name                = "prl-xml",
     .instance_size              = sizeof(BDRVPrlXmlState),
+    .bdrv_probe                 = prl_probe_xml,
     .bdrv_open                  = prl_open_xml,
     .bdrv_co_readv              = prl_co_readv,
     .bdrv_co_writev             = prl_co_writev,
-- 
2.21.3