From a484a93b290806d01850e58905d65bc798b4cd91 Mon Sep 17 00:00:00 2001
From: Jeff Epler <jepler@gmail.com>
Date: Fri, 29 Nov 2019 08:15:29 -0600
Subject: [PATCH] nRF: disk_read must be 4-byte aligned

.. a requirement that oofatfs needs to be taught to respect.

This problem can be demonstrated with the following snippet, except
that the related file ("test.bin") must also be contiguous on the
filesystem.  You can ensure this by reformatting your device's filesystem
before testing, then copying any single file bigger than 4kB to test.bin.

    f = open("test.bin", "rb")
    f.seek(2048)
    b = bytearray(2048)
    v = memoryview(b)
    f.readinto(v[909:])

Closes: #2332
---
 lib/oofatfs/ff.c     | 6 +++++-
 lib/oofatfs/ffconf.h | 6 ++++++
 ports/nrf/Makefile   | 1 +
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/lib/oofatfs/ff.c b/lib/oofatfs/ff.c
index b0984756bf..71bd19702a 100644
--- a/lib/oofatfs/ff.c
+++ b/lib/oofatfs/ff.c
@@ -3382,7 +3382,11 @@ FRESULT f_read (
             if (!sect) ABORT(fs, FR_INT_ERR);
             sect += csect;
             cc = btr / SS(fs);                  /* When remaining bytes >= sector size, */
-            if (cc) {                           /* Read maximum contiguous sectors directly */
+            if (cc
+#if _FS_DISK_READ_ALIGNED
+                    && (((int)rbuff & 3) == 0)
+#endif
+                    ) {/* Read maximum contiguous sectors directly */
                 if (csect + cc > fs->csize) {   /* Clip at cluster boundary */
                     cc = fs->csize - csect;
                 }
diff --git a/lib/oofatfs/ffconf.h b/lib/oofatfs/ffconf.h
index 214311b4c2..a3795fa3fe 100644
--- a/lib/oofatfs/ffconf.h
+++ b/lib/oofatfs/ffconf.h
@@ -343,6 +343,12 @@
 /  SemaphoreHandle_t and etc.. A header file for O/S definitions needs to be
 /  included somewhere in the scope of ff.h. */
 
+// Set to nonzero if buffers passed to disk_read have a word alignment
+// restriction
+#ifndef _FS_DISK_READ_ALIGNED
+#define _FS_DISK_READ_ALIGNED 0
+#endif
+
 /* #include <windows.h> // O/S definitions  */
 
 
diff --git a/ports/nrf/Makefile b/ports/nrf/Makefile
index be8a71b3f3..096dfaa4bf 100755
--- a/ports/nrf/Makefile
+++ b/ports/nrf/Makefile
@@ -106,6 +106,7 @@ CFLAGS += -Wno-undef
 CFLAGS += -Wno-cast-align
 
 NRF_DEFINES += -DCONFIG_GPIO_AS_PINRESET
+NRF_DEFINES += -D_FS_DISK_READ_ALIGNED=1
 CFLAGS += $(NRF_DEFINES)
 
 CFLAGS += \