ports/embed: Enable use of POSIX VFS.

In the embedding-full example, that requires disabling mphal-backed stdio
again as it conflicts with the implementation brought in by
vfs_posix_file.c.

Signed-off-by: Christian Walther <cwalther@gmx.ch>

examples/embedding-full/main.c

@@ -28,8 +28,15 @@ static const char *example_2 =
     "help('modules')\n"
     "import sys\n"
     "help(sys)\n"
+    // Skip testing stdin when using the POSIX implementation, i.e. it is
+    // connected to actual stdin, because that makes the program wait for input,
+    // which can be inconvenient or confusing (giving the appearance of being
+    // stuck). There is no harm enabling it if you remember to provide some
+    // input.
+#if !MICROPY_VFS_POSIX
     "print('sys.stdin.read(3):', repr(sys.stdin.read(3)))\n"
     "print('sys.stdin.buffer.read(3):', repr(sys.stdin.buffer.read(3)))\n"
+#endif
     "sys.stdout.write('hello stdout text\\n')\n"
     "sys.stdout.buffer.write(b'hello stdout binary\\n')\n"
     "sys.stdout.write('hello stderr text\\n')\n"
@@ -61,12 +68,23 @@ static const char *example_2 =
     "import lfshello\n"
     "help(lfshello)\n"
     "print('lfshello.hello():', lfshello.hello())\n"
+    "vfs.mount(vfs.VfsPosix('.'), '/posix')\n"
+    "print('os.listdir(\\'/posix\\'):', os.listdir('/posix'))\n"
+    "with open('/posix/posixhello.py', 'wb') as f:\n"
+    "    f.write(b'def hello():\\n    return \"Hello from a POSIX file!\"\\n')\n"
+    "with open('/posix/posixhello.py', 'rb') as f:\n"
+    "    print('posixhello.py:', f.read())\n"
+    "sys.path.append('/posix')\n"
+    "import posixhello\n"
+    "help(posixhello)\n"
+    "print('posixhello.hello():', posixhello.hello())\n"
+    "os.unlink('/posix/posixhello.py')"
     "\n"
     "print('finish')\n"
     ;
 
 // This array is the MicroPython GC heap.
-static char heap[12 * 1024];
+static char heap[16 * 1024];
 
 int main() {
 #if MICROPY_STACK_CHECK

examples/embedding-full/micropython_embed.mk

@@ -16,8 +16,8 @@ EMBED_EXTRA += \
 
 # Include source for mphal-backed stdio in the output.
 # Disable when using POSIX-backed stdio (MICROPY_VFS_POSIX).
-EMBED_EXTRA += \
-	shared/runtime/sys_stdio_mphal.c
+#EMBED_EXTRA += \
+#	shared/runtime/sys_stdio_mphal.c
 
 # Include library sources for littlefs 2 in the output.
 EMBED_EXTRA += littlefs2

examples/embedding-full/mpconfigport.h

@@ -19,9 +19,11 @@
 #define MICROPY_HW_BOARD_NAME                   "embedded"
 #define MICROPY_HW_MCU_NAME                     "C"
 
-// Enable the VFS subsystem, littlefs, importing from VFS, and the vfs module.
+// Enable the VFS subsystem, littlefs and POSIX VFS, importing from VFS, and
+// the vfs module.
 #define MICROPY_VFS                             (1)
 #define MICROPY_VFS_LFS2                        (1)
+#define MICROPY_VFS_POSIX                       (1)
 #define MICROPY_READER_VFS                      (1)
 #define MICROPY_PY_VFS                          (1)
 

examples/embedding-full/mphal.c

@@ -65,6 +65,8 @@ uint64_t mp_hal_time_ns(void) {
 #endif
 
 // Text-mode standard output
+// (When MICROPY_PY_SYS_STDFILES && MICROPY_VFS_POSIX, this is only used for
+// mp_plat_print (mostly debug output), but not for print() and sys.stdout.)
 void mp_hal_stdout_tx_strn_cooked(const char *str, size_t len) {
     // This is a simplistic implementation for demonstration purposes. A real
     // one would probably want to prefix every line, not just at the start of a
@@ -75,7 +77,7 @@ void mp_hal_stdout_tx_strn_cooked(const char *str, size_t len) {
     start_of_line = (len > 0 && (str[len-1] == '\n' || str[len-1] == '\r'));
 }
 
-#if MICROPY_PY_SYS_STDFILES
+#if MICROPY_PY_SYS_STDFILES && !MICROPY_VFS_POSIX
 
 // Binary-mode standard input
 // Receive single character, blocking until one is available.

ports/embed/port/mphalport.h

@@ -4,3 +4,23 @@
 #if MICROPY_KBD_EXCEPTION
 void mp_hal_set_interrupt_char(int c);
 #endif
+
+#if MICROPY_VFS_POSIX
+// This macro is used to implement PEP 475 to retry specified syscalls on EINTR
+#define MP_HAL_RETRY_SYSCALL(ret, syscall, raise) { \
+        for (;;) { \
+            MP_THREAD_GIL_EXIT(); \
+            ret = syscall; \
+            MP_THREAD_GIL_ENTER(); \
+            if (ret == -1) { \
+                int err = errno; \
+                if (err == EINTR) { \
+                    mp_handle_pending(true); \
+                    continue; \
+                } \
+                raise; \
+            } \
+            break; \
+        } \
+}
+#endif