ubiattach: fail if kernel ignores max_beb_per1024

If the kernel doesn't know the max_beb_per1024 parameter in the attach
ioctl, but the call still succeeded ubi_attach and ubi_attach_mtd will
return 1 instead of 0.

In this case, the ubiattach command will detach the device and fail with
an error message.

Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

3 files changed, 43 insertions, 6 deletions

diff --git a/ubi-utils/include/libubi.h b/ubi-utils/include/libubi.h
index 84ac84c..47f40e2 100644
--- a/ubi-utils/include/libubi.h
+++ b/ubi-utils/include/libubi.h
@@ -221,12 +221,14 @@ int mtd_num2ubi_dev(libubi_t desc, int mtd_num, int *dev_num);
  * @req. If @req->mtd_dev_node is given it should contain path to the MTD
  * device node. Otherwise @req->mtd_num will be used.
  *
- * Returns %0 in case of success and %-1 in case of failure (errno is set).
- * The newly created UBI device number is returned in @req->dev_num.
- * The MTD device number is returned in @req->mtd_num (-1 if not found)
+ * Returns %0 in case of success, %-1 in case of failure (errno is set) and %1
+ * if parameter @req->max_beb_per1024 was ignored by kernel (because the kernel
+ * is old and does not support this feature, which was added in 3.7). The newly
+ * created UBI device number is returned in @req->dev_num. In the MTD device
+ * was specified by its device node path, the MTD device number is returned in
+ * @req->mtd_num.
  */
-int ubi_attach(libubi_t desc, const char *node,
-	       struct ubi_attach_request *req);
+int ubi_attach(libubi_t desc, const char *node, struct ubi_attach_request *req);
 
 /**
  * ubi_detach_mtd - detach an MTD device.
diff --git a/ubi-utils/libubi.c b/ubi-utils/libubi.c
index 8e1d3ee..a7463e8 100644
--- a/ubi-utils/libubi.c
+++ b/ubi-utils/libubi.c
@@ -769,6 +769,35 @@ int ubi_attach(libubi_t desc, const char *node, struct ubi_attach_request *req)
 	r.ubi_num = req->dev_num;
 	r.mtd_num = req->mtd_num;
 	r.vid_hdr_offset = req->vid_hdr_offset;
+
+	if (req->max_beb_per1024) {
+		/*
+		 * We first have to check if the running kernel supports the
+		 * 'max_beb_per1024' parameter. To do this, we invoke the
+		 * "attach" ioctl 2 times: first with incorrect value %-1 of
+		 * 'max_beb_per1024'.
+		 *
+		 * If the ioctl succeeds, it means that the kernel doesn't
+		 * support the feature and just ignored our 'max_beb_per1024'
+		 * value.
+		 *
+		 * If the ioctl returns -EINVAL, we assume this is because
+		 * 'max_beb_per1024' was set to -1, and we invoke the ioctl for
+		 * the second time with the 'max_beb_per1024' value.
+		 */
+		r.max_beb_per1024 = -1;
+		ret = do_attach(node, &r);
+		if (ret == 0) {
+			req->dev_num = r.ubi_num;
+			/*
+			 * The call succeeded. It means that the kernel ignored
+			 * 'max_beb_per1024' parameter. 
+			 */
+			return 1;
+		} else if (errno != EINVAL)
+			return ret;
+	}
+
 	r.max_beb_per1024 = req->max_beb_per1024;
 
 	ret = do_attach(node, &r);
diff --git a/ubi-utils/ubiattach.c b/ubi-utils/ubiattach.c
index 8dd0bf6..a7c62d0 100644
--- a/ubi-utils/ubiattach.c
+++ b/ubi-utils/ubiattach.c
@@ -216,12 +216,18 @@ int main(int argc, char * const argv[])
 	req.max_beb_per1024 = args.max_beb_per1024;
 
 	err = ubi_attach(libubi, args.node, &req);
-	if (err) {
+	if (err < 0) {
 		if (args.dev)
 			sys_errmsg("cannot attach \"%s\"", args.dev);
 		else
 			sys_errmsg("cannot attach mtd%d", args.mtdn);
 		goto out_libubi;
+	} else if (err == 1) {
+		/* The kernel did not support the 'max_beb_per1024' parameter */
+		warnmsg("the --max-beb-per1024=%d parameter was ignored", args.max_beb_per1024);
+		normsg("the UBI kernel driver does not support does not allow changing the reserved PEBs count");
+		normsg("the support was added in kernel version 3.7, probably you are running older kernel?");
+		goto out_libubi;
 	}
 
 	/* Print some information about the new UBI device */