extmod/fsusermount: Support mounting of multiple block devices.

This patch adds support to fsusermount for multiple block devices
(instead of just one).  The maximum allowed is fixed at compile time by
the size of the fs_user_mount array accessed via MP_STATE_PORT, which
in turn is set by MICROPY_FATFS_VOLUMES.

With this patch, stmhal (which is still tightly coupled to fsusermount)
is also modified to support mounting multiple devices   And the flash and
SD card are now just two block devices that are mounted at start up if
they exist (and they have special native code to make them more
efficient).

2 files changed, 52 insertions, 25 deletions

diff --git a/extmod/fsusermount.c b/extmod/fsusermount.c
index 441711ae2..677961ea3 100644
--- a/extmod/fsusermount.c
+++ b/extmod/fsusermount.c
@@ -53,25 +53,38 @@ STATIC mp_obj_t fatfs_mount_mkfs(mp_uint_t n_args, const mp_obj_t *pos_args, mp_
     if (device == mp_const_none) {
         // umount
         FRESULT res = FR_NO_FILESYSTEM;
-        if (MP_STATE_PORT(fs_user_mount) != NULL) {
-            res = f_mount(NULL, MP_STATE_PORT(fs_user_mount)->str, 0);
-            m_del_obj(fs_user_mount_t, MP_STATE_PORT(fs_user_mount));
-            MP_STATE_PORT(fs_user_mount) = NULL;
+        for (size_t i = 0; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
+            fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
+            if (vfs != NULL && !memcmp(mnt_str, vfs->str, mnt_len + 1)) {
+                res = f_mount(NULL, vfs->str, 0);
+                if (vfs->flags & FSUSER_FREE_OBJ) {
+                    m_del_obj(fs_user_mount_t, vfs);
+                }
+                MP_STATE_PORT(fs_user_mount)[i] = NULL;
+                break;
+            }
         }
         if (res != FR_OK) {
             nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "can't umount"));
         }
     } else {
         // mount
-        if (MP_STATE_PORT(fs_user_mount) != NULL) {
-            nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "device already mounted"));
+        size_t i = 0;
+        for (; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
+            if (MP_STATE_PORT(fs_user_mount)[i] == NULL) {
+                break;
+            }
+        }
+        if (i == MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount))) {
+            nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "too many devices mounted"));
         }
 
         // create new object
         fs_user_mount_t *vfs;
-        MP_STATE_PORT(fs_user_mount) = vfs = m_new_obj(fs_user_mount_t);
+        MP_STATE_PORT(fs_user_mount)[i] = vfs = m_new_obj(fs_user_mount_t);
         vfs->str = mnt_str;
         vfs->len = mnt_len;
+        vfs->flags = FSUSER_FREE_OBJ;
 
         // load block protocol methods
         mp_load_method(device, MP_QSTR_readblocks, vfs->readblocks);
@@ -79,7 +92,7 @@ STATIC mp_obj_t fatfs_mount_mkfs(mp_uint_t n_args, const mp_obj_t *pos_args, mp_
         mp_load_method_maybe(device, MP_QSTR_ioctl, vfs->u.ioctl);
         if (vfs->u.ioctl[0] != MP_OBJ_NULL) {
             // device supports new block protocol, so indicate it
-            vfs->u.old.count[1] = MP_OBJ_SENTINEL;
+            vfs->flags |= FSUSER_HAVE_IOCTL;
         } else {
             // no ioctl method, so assume the device uses the old block protocol
             mp_load_method_maybe(device, MP_QSTR_sync, vfs->u.old.sync);
@@ -114,7 +127,7 @@ mkfs_error:
                 if (res != FR_OK) {
                     goto mkfs_error;
                 }
-                MP_STATE_PORT(fs_user_mount) = NULL;
+                MP_STATE_PORT(fs_user_mount)[i] = NULL;
             }
         } else {
             nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "can't mount"));
@@ -141,30 +154,39 @@ STATIC mp_obj_t fatfs_mount(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t
 MP_DEFINE_CONST_FUN_OBJ_KW(fsuser_mount_obj, 2, fatfs_mount);
 
 STATIC mp_obj_t fatfs_umount(mp_obj_t bdev_or_path_in) {
-    if (MP_STATE_PORT(fs_user_mount) == NULL) {
-        goto einval;
-    }
-
+    size_t i = 0;
     if (MP_OBJ_IS_STR(bdev_or_path_in)) {
         mp_uint_t mnt_len;
         const char *mnt_str = mp_obj_str_get_data(bdev_or_path_in, &mnt_len);
-        if (memcmp(mnt_str, MP_STATE_PORT(fs_user_mount)->str, mnt_len + 1)) {
-            goto einval;
+        for (; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
+            fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
+            if (!memcmp(mnt_str, vfs->str, mnt_len + 1)) {
+                break;
+            }
         }
-    } else if (bdev_or_path_in != MP_STATE_PORT(fs_user_mount)->readblocks[1]) {
-        goto einval;
+    } else {
+        for (; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
+            fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
+            if (bdev_or_path_in == vfs->readblocks[1]) {
+                break;
+            }
+        }
+    }
+
+    if (i == MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount))) {
+        nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(EINVAL)));
     }
 
-    FRESULT res = f_mount(NULL, MP_STATE_PORT(fs_user_mount)->str, 0);
-    m_del_obj(fs_user_mount_t, MP_STATE_PORT(fs_user_mount));
-    MP_STATE_PORT(fs_user_mount) = NULL;
+    fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
+    FRESULT res = f_mount(NULL, vfs->str, 0);
+    if (vfs->flags & FSUSER_FREE_OBJ) {
+        m_del_obj(fs_user_mount_t, vfs);
+    }
+    MP_STATE_PORT(fs_user_mount)[i] = NULL;
     if (res != FR_OK) {
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "can't umount"));
     }
     return mp_const_none;
-
-einval:
-        nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(EINVAL)));
 }
 MP_DEFINE_CONST_FUN_OBJ_1(fsuser_umount_obj, fatfs_umount);
 
diff --git a/extmod/fsusermount.h b/extmod/fsusermount.h
index 0fa353b7e..3dcd03591 100644
--- a/extmod/fsusermount.h
+++ b/extmod/fsusermount.h
@@ -24,13 +24,18 @@
  * THE SOFTWARE.
  */
 
+// these are the values for fs_user_mount_t.flags
+#define FSUSER_NATIVE       (0x0001) // readblocks[2]/writeblocks[2] contain native func
+#define FSUSER_FREE_OBJ     (0x0002) // fs_user_mount_t obj should be freed on umount
+#define FSUSER_HAVE_IOCTL   (0x0004) // new protocol with ioctl
+
 typedef struct _fs_user_mount_t {
     const char *str;
-    mp_uint_t len;
+    uint16_t len; // length of str
+    uint16_t flags;
     mp_obj_t readblocks[4];
     mp_obj_t writeblocks[4];
     // new protocol uses just ioctl, old uses sync (optional) and count
-    // if ioctl[3]=count[1]=MP_OBJ_SENTINEL then we have the new protocol, else old
     union {
         mp_obj_t ioctl[4];
         struct {