usb-mtp: Support delete of mtp objects

Write of existing objects by the initiator is acheived by
making a temporary buffer with the new changes, deleting the
old file and then writing a new file with the same name.

Also, add a "readonly" property which needs to be set to false
for deletion to work.

Signed-off-by: Bandan Das <bsd@redhat.com>
Message-id: 20180223164829.29683-4-bsd@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/usb/dev-mtp.c

@@ -46,6 +46,7 @@ enum mtp_code {
     CMD_GET_OBJECT_HANDLES         = 0x1007,
     CMD_GET_OBJECT_INFO            = 0x1008,
     CMD_GET_OBJECT                 = 0x1009,
+    CMD_DELETE_OBJECT              = 0x100b,
     CMD_GET_PARTIAL_OBJECT         = 0x101b,
     CMD_GET_OBJECT_PROPS_SUPPORTED = 0x9801,
     CMD_GET_OBJECT_PROP_DESC       = 0x9802,
@@ -62,6 +63,8 @@ enum mtp_code {
     RES_INVALID_STORAGE_ID         = 0x2008,
     RES_INVALID_OBJECT_HANDLE      = 0x2009,
     RES_INVALID_OBJECT_FORMAT_CODE = 0x200b,
+    RES_STORE_READ_ONLY            = 0x200e,
+    RES_PARTIAL_DELETE             = 0x2012,
     RES_SPEC_BY_FORMAT_UNSUPPORTED = 0x2014,
     RES_INVALID_PARENT_OBJECT      = 0x201a,
     RES_INVALID_PARAMETER          = 0x201d,
@@ -172,6 +175,7 @@ struct MTPState {
     MTPControl   *result;
     uint32_t     session;
     uint32_t     next_handle;
+    bool         readonly;
 
     QTAILQ_HEAD(, MTPObject) objects;
 #ifdef CONFIG_INOTIFY1
@@ -799,6 +803,7 @@ static MTPData *usb_mtp_get_device_info(MTPState *s, MTPControl *c)
         CMD_GET_NUM_OBJECTS,
         CMD_GET_OBJECT_HANDLES,
         CMD_GET_OBJECT_INFO,
+        CMD_DELETE_OBJECT,
         CMD_GET_OBJECT,
         CMD_GET_PARTIAL_OBJECT,
         CMD_GET_OBJECT_PROPS_SUPPORTED,
@@ -1113,6 +1118,116 @@ static MTPData *usb_mtp_get_object_prop_value(MTPState *s, MTPControl *c,
     return d;
 }
 
+/* Return correct return code for a delete event */
+enum {
+    ALL_DELETE,
+    PARTIAL_DELETE,
+    READ_ONLY,
+};
+
+/* Assumes that children, if any, have been already freed */
+static void usb_mtp_object_free_one(MTPState *s, MTPObject *o)
+{
+#ifndef CONFIG_INOTIFY1
+    assert(o->nchildren == 0);
+    QTAILQ_REMOVE(&s->objects, o, next);
+    g_free(o->name);
+    g_free(o->path);
+    g_free(o);
+#endif
+}
+
+static int usb_mtp_deletefn(MTPState *s, MTPObject *o, uint32_t trans)
+{
+    MTPObject *iter, *iter2;
+    bool partial_delete = false;
+    bool success = false;
+
+    /*
+     * TODO: Add support for Protection Status
+     */
+
+    QLIST_FOREACH(iter, &o->children, list) {
+        if (iter->format == FMT_ASSOCIATION) {
+            QLIST_FOREACH(iter2, &iter->children, list) {
+                usb_mtp_deletefn(s, iter2, trans);
+            }
+        }
+    }
+
+    if (o->format == FMT_UNDEFINED_OBJECT) {
+        if (remove(o->path)) {
+            partial_delete = true;
+        } else {
+            usb_mtp_object_free_one(s, o);
+            success = true;
+        }
+    }
+
+    if (o->format == FMT_ASSOCIATION) {
+        if (rmdir(o->path)) {
+            partial_delete = true;
+        } else {
+            usb_mtp_object_free_one(s, o);
+            success = true;
+        }
+    }
+
+    if (success && partial_delete) {
+        return PARTIAL_DELETE;
+    }
+    if (!success && partial_delete) {
+        return READ_ONLY;
+    }
+    return ALL_DELETE;
+}
+
+static void usb_mtp_object_delete(MTPState *s, uint32_t handle,
+                                  uint32_t format_code, uint32_t trans)
+{
+    MTPObject *o;
+    int ret;
+
+    /* Return error if store is read-only */
+    if (!FLAG_SET(s, MTP_FLAG_WRITABLE)) {
+        usb_mtp_queue_result(s, RES_STORE_READ_ONLY,
+                             trans, 0, 0, 0, 0);
+        return;
+    }
+
+    if (format_code != 0) {
+        usb_mtp_queue_result(s, RES_SPEC_BY_FORMAT_UNSUPPORTED,
+                             trans, 0, 0, 0, 0);
+        return;
+    }
+
+    if (handle == 0xFFFFFFF) {
+        o = QTAILQ_FIRST(&s->objects);
+    } else {
+        o = usb_mtp_object_lookup(s, handle);
+    }
+    if (o == NULL) {
+        usb_mtp_queue_result(s, RES_INVALID_OBJECT_HANDLE,
+                             trans, 0, 0, 0, 0);
+        return;
+    }
+
+    ret = usb_mtp_deletefn(s, o, trans);
+    if (ret == PARTIAL_DELETE) {
+        usb_mtp_queue_result(s, RES_PARTIAL_DELETE,
+                             trans, 0, 0, 0, 0);
+        return;
+    } else if (ret == READ_ONLY) {
+        usb_mtp_queue_result(s, RES_STORE_READ_ONLY, trans,
+                             0, 0, 0, 0);
+        return;
+    } else {
+        usb_mtp_queue_result(s, RES_OK, trans,
+                             0, 0, 0, 0);
+        return;
+    }
+}
+
 static void usb_mtp_command(MTPState *s, MTPControl *c)
 {
     MTPData *data_in = NULL;
@@ -1239,6 +1354,9 @@ static void usb_mtp_command(MTPState *s, MTPControl *c)
             return;
         }
         break;
+    case CMD_DELETE_OBJECT:
+        usb_mtp_object_delete(s, c->argv[0], c->argv[1], c->trans);
+        return;
     case CMD_GET_PARTIAL_OBJECT:
         o = usb_mtp_object_lookup(s, c->argv[0]);
         if (o == NULL) {
@@ -1545,6 +1663,10 @@ static void usb_mtp_realize(USBDevice *dev, Error **errp)
             return;
         }
         s->desc = strrchr(s->root, '/');
+        /* Mark store as RW */
+        if (!s->readonly) {
+            s->flags |= (1 << MTP_FLAG_WRITABLE);
+        }
         if (s->desc && s->desc[0]) {
             s->desc = g_strdup(s->desc + 1);
         } else {
@@ -1567,6 +1689,7 @@ static const VMStateDescription vmstate_usb_mtp = {
 static Property mtp_properties[] = {
     DEFINE_PROP_STRING("x-root", MTPState, root),
     DEFINE_PROP_STRING("desc", MTPState, desc),
+    DEFINE_PROP_BOOL("readonly", MTPState, readonly, true),
     DEFINE_PROP_END_OF_LIST(),
 };