Add option to disable the concurrent write protection

This allows writing to the filesystem from the host computer and
CircuitPython by increasing the risk of filesystem corruption.

3 files changed, 32 insertions, 24 deletions

diff --git a/supervisor/shared/filesystem.c b/supervisor/shared/filesystem.c
index 3382d28be..0ef978ef2 100644
--- a/supervisor/shared/filesystem.c
+++ b/supervisor/shared/filesystem.c
@@ -24,6 +24,8 @@
  * THE SOFTWARE.
  */
 
+#include "supervisor/filesystem.h"
+
 #include "extmod/vfs_fat.h"
 #include "lib/oofatfs/ff.h"
 #include "lib/oofatfs/diskio.h"
@@ -92,16 +94,42 @@ void filesystem_flush(void) {
     supervisor_flash_flush();
 }
 
-void filesystem_writable_by_python(bool writable) {
+void filesystem_set_internal_writable_by_usb(bool writable) {
     fs_user_mount_t *vfs = &_internal_vfs;
 
-    if (!writable) {
+    filesystem_set_writable_by_usb(vfs, writable);
+}
+
+void filesystem_set_writable_by_usb(fs_user_mount_t *vfs, bool usb_writable) {
+    if (usb_writable) {
         vfs->flags |= FSUSER_USB_WRITABLE;
     } else {
         vfs->flags &= ~FSUSER_USB_WRITABLE;
     }
 }
 
+bool filesystem_is_writable_by_python(fs_user_mount_t *vfs) {
+    return (vfs->flags & FSUSER_CONCURRENT_WRITE_PROTECTED) == 0 ||
+           (vfs->flags & FSUSER_USB_WRITABLE) == 0;
+}
+
+bool filesystem_is_writable_by_usb(fs_user_mount_t *vfs) {
+    return (vfs->flags & FSUSER_CONCURRENT_WRITE_PROTECTED) == 0 ||
+           (vfs->flags & FSUSER_USB_WRITABLE) != 0;
+}
+
+void filesystem_set_internal_concurrent_write_protection(bool concurrent_write_protection) {
+    filesystem_set_concurrent_write_protection(&_internal_vfs, concurrent_write_protection);
+}
+
+void filesystem_set_concurrent_write_protection(fs_user_mount_t *vfs, bool concurrent_write_protection) {
+    if (concurrent_write_protection) {
+        vfs->flags |= FSUSER_CONCURRENT_WRITE_PROTECTED;
+    } else {
+        vfs->flags &= ~FSUSER_CONCURRENT_WRITE_PROTECTED;
+    }
+}
+
 bool filesystem_present(void) {
     return true;
 }
diff --git a/supervisor/shared/flash.c b/supervisor/shared/flash.c
index 8be21e5d0..6b1f24b4b 100644
--- a/supervisor/shared/flash.c
+++ b/supervisor/shared/flash.c
@@ -33,26 +33,6 @@
 
 #define PART1_START_BLOCK (0x1)
 
-void supervisor_flash_set_usb_writable(bool usb_writable) {
-    mp_vfs_mount_t* current_mount = MP_STATE_VM(vfs_mount_table);
-    for (uint8_t i = 0; current_mount != NULL; i++) {
-        if (i == VFS_INDEX) {
-            break;
-        }
-        current_mount = current_mount->next;
-    }
-    if (current_mount == NULL) {
-        return;
-    }
-    fs_user_mount_t *vfs = (fs_user_mount_t *) current_mount->obj;
-
-    if (usb_writable) {
-        vfs->flags |= FSUSER_USB_WRITABLE;
-    } else {
-        vfs->flags &= ~FSUSER_USB_WRITABLE;
-    }
-}
-
 // there is a singleton Flash object
 const mp_obj_type_t supervisor_flash_type;
 STATIC const mp_obj_base_t supervisor_flash_obj = {&supervisor_flash_type};
diff --git a/supervisor/shared/usb/usb_msc_flash.c b/supervisor/shared/usb/usb_msc_flash.c
index 658aab0d8..f6f0fa9c3 100644
--- a/supervisor/shared/usb/usb_msc_flash.c
+++ b/supervisor/shared/usb/usb_msc_flash.c
@@ -34,6 +34,7 @@
 #include "lib/oofatfs/ff.h"
 #include "py/mpstate.h"
 
+#include "supervisor/filesystem.h"
 #include "supervisor/shared/autoreload.h"
 
 #define MSC_FLASH_BLOCK_SIZE    512
@@ -148,8 +149,7 @@ bool tud_msc_is_writable_cb(uint8_t lun) {
     if (vfs == NULL) {
         return false;
     }
-    if (vfs->writeblocks[0] == MP_OBJ_NULL ||
-        (vfs->flags & FSUSER_USB_WRITABLE) == 0) {
+    if (vfs->writeblocks[0] == MP_OBJ_NULL || !filesystem_is_writable_by_usb(vfs)) {
         return false;
     }
     return true;