linux-kernel - [PATCH] of: base: Change logic in of_alias_get_alias

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Message-Id: <e879d07e97b7f7fc46543315e9fb1b4bc8b7a352.1539001154.git.michal.simek@xilinx.com>
Date:   Mon,  8 Oct 2018 14:19:18 +0200
From:   Michal Simek <michal.simek@...inx.com>
To:     linux-kernel@...r.kernel.org, monstr@...str.eu,
        geert@...ux-m68k.org, gregkh@...uxfoundation.org
Cc:     devicetree@...r.kernel.org, Jiri Slaby <jslaby@...e.com>,
        Rob Herring <robh+dt@...nel.org>, linux-serial@...r.kernel.org,
        Frank Rowand <frowand.list@...il.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] of: base: Change logic in of_alias_get_alias_list()

Check compatible string first before setting up bit in bitmap to also
cover cases that allocated bitfield is not big enough.
Show warning about it but let driver to continue to work with allocated
bitfield to keep at least some devices (included console which
is commonly close to serial0) to work.

Fixes: b1078c355d76 ("of: base: Introduce of_alias_get_alias_list() to check alias IDs")
Fixes: ae1cca3fa347 ("serial: uartps: Change uart ID port allocation")
Signed-off-by: Michal Simek <michal.simek@...inx.com>
---

I have looked at it and I don't think there should be necessary to
report error immediately back with partially initialized bitfield.
The reason is that still there could be a console device which is most
likely below that max limit and it is worth to return at least that nbits
properly filled.
It will also enable cases that you can still continue to use aliases
higher then fields prepared for devices without alias.

To be fixed patches are present in tty-next branch.

---
 drivers/of/base.c                  | 22 ++++++++++++----------
 drivers/tty/serial/xilinx_uartps.c |  2 +-
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 908de45f966b..0b9611e196d1 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1953,13 +1953,15 @@ int of_alias_get_id(struct device_node *np, const char *stem)
  * The function travels the lookup table to record alias ids for the given
  * device match structures and alias stem.
  *
- * Return:	0 or -ENOSYS when !CONFIG_OF
+ * Return:	0 or -ENOSYS when !CONFIG_OF or
+ *		-EINVAL if alias ID is greater then allocated nbits
  */
 int of_alias_get_alias_list(const struct of_device_id *matches,
 			     const char *stem, unsigned long *bitmap,
 			     unsigned int nbits)
 {
 	struct alias_prop *app;
+	int ret = 0;
 
 	/* Zero bitmap field to make sure that all the time it is clean */
 	bitmap_zero(bitmap, nbits);
@@ -1976,21 +1978,21 @@ int of_alias_get_alias_list(const struct of_device_id *matches,
 			continue;
 		}
 
-		if (app->id >= nbits) {
-			pr_debug("%s: ID %d greater then bitmap field %d\n",
-				__func__, app->id, nbits);
-			continue;
-		}
-
 		if (of_match_node(matches, app->np)) {
 			pr_debug("%s: Allocated ID %d\n", __func__, app->id);
-			set_bit(app->id, bitmap);
+
+			if (app->id >= nbits) {
+				pr_warn("%s: ID %d >= than bitmap field %d\n",
+					__func__, app->id, nbits);
+				ret = -EINVAL;
+			} else {
+				set_bit(app->id, bitmap);
+			}
 		}
-		/* Alias exists but is not compatible with matches */
 	}
 	mutex_unlock(&of_mutex);
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(of_alias_get_alias_list);
 
diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index d452dceb0cb3..29a18103182d 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1393,7 +1393,7 @@ static int cdns_get_id(struct platform_device *pdev)
 	if (!alias_bitmap_initialized) {
 		ret = of_alias_get_alias_list(cdns_uart_of_match, "serial",
 					      alias_bitmap, MAX_UART_INSTANCES);
-		if (ret) {
+		if (ret && ret != -EINVAL) {
 			mutex_unlock(&bitmap_lock);
 			return ret;
 		}
-- 
1.9.1