diff --git a/.github/workflows/code_formatting.yml b/.github/workflows/code_formatting.yml
index 9f30f048cfdbe..1972bc6b376c5 100644
--- a/.github/workflows/code_formatting.yml
+++ b/.github/workflows/code_formatting.yml
@@ -3,7 +3,7 @@ name: Check code formatting
 on: [push, pull_request]
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ github.event_name }}
   cancel-in-progress: true
 
 jobs:
diff --git a/.github/workflows/ports_m68kmac.yml b/.github/workflows/ports_m68kmac.yml
index eec7559865f75..15b76f2d082c4 100644
--- a/.github/workflows/ports_m68kmac.yml
+++ b/.github/workflows/ports_m68kmac.yml
@@ -8,7 +8,7 @@ on:
       - created
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ github.event_name }}
   cancel-in-progress: true
 
 jobs:
diff --git a/.github/workflows/ports_unix.yml b/.github/workflows/ports_unix.yml
index 6d885e69d6457..9f5ec001ecbe9 100644
--- a/.github/workflows/ports_unix.yml
+++ b/.github/workflows/ports_unix.yml
@@ -16,57 +16,10 @@ on:
       - 'tests/**'
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ github.event_name }}
   cancel-in-progress: true
 
 jobs:
-  minimal:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - name: Build
-      run: source tools/ci.sh && ci_unix_minimal_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_minimal_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  reproducible:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - name: Build with reproducible date
-      run: source tools/ci.sh && ci_unix_minimal_build
-      env:
-        SOURCE_DATE_EPOCH: 1234567890
-    - name: Check reproducible build date
-      run: echo | ports/unix/build-minimal/micropython -i | grep 'on 2009-02-13;'
-
-  standard:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - name: Build
-      run: source tools/ci.sh && ci_unix_standard_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_standard_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  standard_v2:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - name: Build
-      run: source tools/ci.sh && ci_unix_standard_v2_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_standard_v2_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
   coverage:
     runs-on: ubuntu-latest
     steps:
@@ -113,186 +66,3 @@ jobs:
     - name: Print failures
       if: failure()
       run: tests/run-tests.py --print-failures
-
-  nanbox:
-    runs-on: ubuntu-22.04 # use 22.04 to get python2, and libffi-dev:i386
-    steps:
-    - uses: actions/checkout@v4
-    - name: Install packages
-      run: source tools/ci.sh && ci_unix_32bit_setup
-    - name: Build
-      run: source tools/ci.sh && ci_unix_nanbox_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_nanbox_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  float:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - name: Install packages
-      run: source tools/ci.sh && ci_unix_float_setup
-    - name: Build
-      run: source tools/ci.sh && ci_unix_float_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_float_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  stackless_clang:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - name: Install packages
-      run: source tools/ci.sh && ci_unix_clang_setup
-    - name: Build
-      run: source tools/ci.sh && ci_unix_stackless_clang_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_stackless_clang_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  float_clang:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - name: Install packages
-      run: source tools/ci.sh && ci_unix_clang_setup
-    - name: Build
-      run: source tools/ci.sh && ci_unix_float_clang_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_float_clang_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  settrace_stackless:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - uses: actions/setup-python@v5
-      # Python 3.12 is the default for ubuntu-24.04, but that has compatibility issues with settrace tests.
-      # Can remove this step when ubuntu-latest uses a more recent Python 3.x as the default.
-      with:
-        python-version: '3.11'
-    - name: Build
-      run: source tools/ci.sh && ci_unix_settrace_stackless_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_settrace_stackless_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  macos:
-    runs-on: macos-latest
-    steps:
-    - uses: actions/checkout@v4
-    - uses: actions/setup-python@v5
-      with:
-        python-version: '3.8'
-    - name: Build
-      run: source tools/ci.sh && ci_unix_macos_build
-    - name: Run tests
-      run: source tools/ci.sh && ci_unix_macos_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  qemu_mips:
-    # ubuntu-22.04 is needed for older libffi.
-    runs-on: ubuntu-22.04
-    steps:
-    - uses: actions/checkout@v4
-    - name: Install packages
-      run: source tools/ci.sh && ci_unix_qemu_mips_setup
-    - name: Build
-      run: source tools/ci.sh && ci_unix_qemu_mips_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_qemu_mips_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  qemu_arm:
-    # ubuntu-22.04 is needed for older libffi.
-    runs-on: ubuntu-22.04
-    steps:
-    - uses: actions/checkout@v4
-    - name: Install packages
-      run: source tools/ci.sh && ci_unix_qemu_arm_setup
-    - name: Build
-      run: source tools/ci.sh && ci_unix_qemu_arm_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_qemu_arm_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  qemu_riscv64:
-    # ubuntu-22.04 is needed for older libffi.
-    runs-on: ubuntu-22.04
-    steps:
-    - uses: actions/checkout@v4
-    - name: Install packages
-      run: source tools/ci.sh && ci_unix_qemu_riscv64_setup
-    - name: Build
-      run: source tools/ci.sh && ci_unix_qemu_riscv64_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_qemu_riscv64_run_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  sanitize_address:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - uses: actions/setup-python@v5
-      # Python 3.12 is the default for ubuntu-24.04, but that has compatibility issues with settrace tests.
-      # Can remove this step when ubuntu-latest uses a more recent Python 3.x as the default.
-      with:
-        python-version: '3.11'
-    - name: Install packages
-      run: source tools/ci.sh && ci_unix_coverage_setup
-    - name: Build
-      run: source tools/ci.sh && ci_unix_sanitize_address_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_sanitize_address_run_tests
-    - name: Test merging .mpy files
-      run: source tools/ci.sh && ci_unix_coverage_run_mpy_merge_tests
-    - name: Build native mpy modules
-      run: source tools/ci.sh && ci_native_mpy_modules_build
-    - name: Test importing .mpy generated by mpy_ld.py
-      run: source tools/ci.sh && ci_unix_coverage_run_native_mpy_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
-
-  sanitize_undefined:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - uses: actions/setup-python@v5
-      # Python 3.12 is the default for ubuntu-24.04, but that has compatibility issues with settrace tests.
-      # Can remove this step when ubuntu-latest uses a more recent Python 3.x as the default.
-      with:
-        python-version: '3.11'
-    - name: Install packages
-      run: source tools/ci.sh && ci_unix_coverage_setup
-    - name: Build
-      run: source tools/ci.sh && ci_unix_sanitize_undefined_build
-    - name: Run main test suite
-      run: source tools/ci.sh && ci_unix_sanitize_undefined_run_tests
-    - name: Test merging .mpy files
-      run: source tools/ci.sh && ci_unix_coverage_run_mpy_merge_tests
-    - name: Build native mpy modules
-      run: source tools/ci.sh && ci_native_mpy_modules_build
-    - name: Test importing .mpy generated by mpy_ld.py
-      run: source tools/ci.sh && ci_unix_coverage_run_native_mpy_tests
-    - name: Print failures
-      if: failure()
-      run: tests/run-tests.py --print-failures
diff --git a/extmod/moductypes.c b/extmod/moductypes.c
index 4ba3fb7146b47..d0c3178a9fe16 100644
--- a/extmod/moductypes.c
+++ b/extmod/moductypes.c
@@ -48,13 +48,21 @@ static const mp_obj_type_t uctypes_struct_type;
 // Get size of any type descriptor
 static mp_uint_t uctypes_struct_size(mp_obj_t desc_in, int layout_type, mp_uint_t *max_field_size);
 
+#define CTYPES_FLAGS_SIZE_BITS (2)
+#define CTYPES_OFFSET_SIZE_BITS (8 * sizeof(uint32_t) - 2)
+
 typedef struct _mp_obj_uctypes_struct_t {
     mp_obj_base_t base;
     mp_obj_t desc;
-    byte *addr;
-    uint32_t flags;
+    byte *ptrbase;
+    uint32_t flags : CTYPES_FLAGS_SIZE_BITS;
+    uint32_t offset : CTYPES_OFFSET_SIZE_BITS;
 } mp_obj_uctypes_struct_t;
 
+static inline byte *struct_addr(mp_obj_uctypes_struct_t *s) {
+    return s->ptrbase + s->offset;
+}
+
 static MP_NORETURN void syntax_error(void) {
     mp_raise_TypeError(MP_ERROR_TEXT("syntax error in uctypes descriptor"));
 }
@@ -80,10 +88,12 @@ mp_obj_t uctypes_struct_make_new(const mp_obj_type_t *type, size_t n_args, size_
     }
     mp_buffer_info_t bufinfo;
     mp_obj_uctypes_struct_t *o = mp_obj_malloc(mp_obj_uctypes_struct_t, type);
-    if (mp_get_buffer(args[0], &bufinfo, MP_BUFFER_READ)) {
-        o->addr = bufinfo.buf;
+    if (mp_get_buffer(args[0], &bufinfo, MP_BUFFER_READ | MP_BUFFER_GET_BASE)) {
+        o->ptrbase = bufinfo.base;
+        o->offset = (char *)bufinfo.buf - (char *)bufinfo.base;
     } else {
-        o->addr = (void *)(uintptr_t)mp_obj_get_int_truncated(args[0]);
+        o->ptrbase = (void *)(uintptr_t)mp_obj_get_int_truncated(args[0]);
+        o->offset = 0;
     }
     o->desc = desc;
     o->flags = flags;
@@ -107,9 +117,8 @@ mp_obj_t uctypes_struct_type_make_new(const mp_obj_type_t *type_in, size_t n_arg
     mp_uint_t size = uctypes_struct_size(desc, type->struct_flags, &max_field_size);
 
     mp_buffer_info_t bufinfo;
-    mp_obj_t bytearray = mp_obj_new_bytearray(size, NULL);
-    mp_get_buffer_raise(bytearray, &bufinfo, MP_BUFFER_WRITE);
     if (is_ptr(desc)) {
+        bufinfo.len = size;
         if (n_args != 1) {
             mp_raise_TypeError(NULL);
         }
@@ -121,6 +130,9 @@ mp_obj_t uctypes_struct_type_make_new(const mp_obj_type_t *type_in, size_t n_arg
             mp_get_buffer_raise(args[0], &pointee, MP_BUFFER_WRITE);
             *(void **)bufinfo.buf = pointee.buf;
         }
+    } else {
+        mp_obj_t bytearray = mp_obj_new_bytearray(size, NULL);
+        mp_get_buffer_raise(bytearray, &bufinfo, MP_BUFFER_WRITE);
     }
 
     mp_obj_t args1[] = {mp_obj_new_int((intptr_t)bufinfo.buf), desc, mp_obj_new_int(type->struct_flags)};
@@ -180,7 +192,7 @@ void uctypes_struct_print(const mp_print_t *print, mp_obj_t self_in, mp_print_ki
         typen = "ERROR";
     }
 
-    mp_printf(print, "<%q %s %p>", (qstr)mp_obj_get_type_qstr(self_in), typen, self->addr);
+    mp_printf(print, "<%q %s %p>", (qstr)mp_obj_get_type_qstr(self_in), typen, struct_addr(self));
 }
 
 // Get size of scalar type descriptor
@@ -477,16 +489,16 @@ static mp_obj_t uctypes_struct_attr_op(mp_obj_t self_in, qstr attr, mp_obj_t set
         if (val_type <= INT64 || val_type == FLOAT32 || val_type == FLOAT64) {
             if (self->flags == LAYOUT_NATIVE) {
                 if (set_val == MP_OBJ_NULL) {
-                    return get_aligned(val_type, self->addr + offset, 0);
+                    return get_aligned(val_type, struct_addr(self) + offset, 0);
                 } else {
-                    set_aligned(val_type, self->addr + offset, 0, set_val);
+                    set_aligned(val_type, struct_addr(self) + offset, 0, set_val);
                     return set_val; // just !MP_OBJ_NULL
                 }
             } else {
                 if (set_val == MP_OBJ_NULL) {
-                    return get_unaligned(val_type, self->addr + offset, self->flags);
+                    return get_unaligned(val_type, struct_addr(self) + offset, self->flags);
                 } else {
-                    set_unaligned(val_type, self->addr + offset, self->flags, set_val);
+                    set_unaligned(val_type, struct_addr(self) + offset, self->flags, set_val);
                     return set_val; // just !MP_OBJ_NULL
                 }
             }
@@ -496,9 +508,9 @@ static mp_obj_t uctypes_struct_attr_op(mp_obj_t self_in, qstr attr, mp_obj_t set
             offset &= (1 << OFFSET_BITS) - 1;
             mp_uint_t val;
             if (self->flags == LAYOUT_NATIVE) {
-                val = get_aligned_basic(val_type & 6, self->addr + offset);
+                val = get_aligned_basic(val_type & 6, struct_addr(self) + offset);
             } else {
-                val = mp_binary_get_int(GET_SCALAR_SIZE(val_type & 7), val_type & 1, self->flags, self->addr + offset);
+                val = mp_binary_get_int(GET_SCALAR_SIZE(val_type & 7), val_type & 1, self->flags, struct_addr(self) + offset);
             }
             if (set_val == MP_OBJ_NULL) {
                 val >>= bit_offset;
@@ -515,10 +527,10 @@ static mp_obj_t uctypes_struct_attr_op(mp_obj_t self_in, qstr attr, mp_obj_t set
                 val = (val & ~mask) | set_val_int;
 
                 if (self->flags == LAYOUT_NATIVE) {
-                    set_aligned_basic(val_type & 6, self->addr + offset, val);
+                    set_aligned_basic(val_type & 6, struct_addr(self) + offset, val);
                 } else {
                     mp_binary_set_int(GET_SCALAR_SIZE(val_type & 7), self->flags == LAYOUT_BIG_ENDIAN,
-                        self->addr + offset, val);
+                        struct_addr(self) + offset, val);
                 }
                 return set_val; // just !MP_OBJ_NULL
             }
@@ -544,19 +556,19 @@ static mp_obj_t uctypes_struct_attr_op(mp_obj_t self_in, qstr attr, mp_obj_t set
 
     switch (agg_type) {
         case STRUCT: {
-            mp_obj_t args[] = { mp_obj_new_int((mp_uint_t)(uintptr_t)self->addr + offset), sub->items[1], mp_obj_new_int(self->flags) };
+            mp_obj_t args[] = { mp_obj_new_int((mp_uint_t)(uintptr_t)struct_addr(self) + offset), sub->items[1], mp_obj_new_int(self->flags) };
             return uctypes_struct_make_new(&uctypes_struct_type, MP_ARRAY_SIZE(args), 0, args);
         }
         case ARRAY: {
             mp_uint_t dummy;
             if (IS_SCALAR_ARRAY(sub) && IS_SCALAR_ARRAY_OF_BYTES(sub)) {
-                return mp_obj_new_bytearray_by_ref(uctypes_struct_agg_size(sub, self->flags, &dummy), self->addr + offset);
+                return mp_obj_new_bytearray_by_ref(uctypes_struct_agg_size(sub, self->flags, &dummy), struct_addr(self) + offset);
             }
             // Fall thru to return uctypes struct object
             MP_FALLTHROUGH
         }
         case PTR: {
-            mp_obj_t args[] = { mp_obj_new_int((mp_uint_t)(uintptr_t)self->addr + offset), deref, mp_obj_new_int(self->flags) };
+            mp_obj_t args[] = { mp_obj_new_int((mp_uint_t)(uintptr_t)struct_addr(self) + offset), deref, mp_obj_new_int(self->flags) };
             return uctypes_struct_make_new(&uctypes_struct_type, MP_ARRAY_SIZE(args), 0, args);
         }
     }
@@ -640,13 +652,13 @@ mp_obj_t uctypes_struct_subscr(mp_obj_t self_in, mp_obj_t index_in, mp_obj_t val
                 // array of scalars
                 if (self->flags == LAYOUT_NATIVE) {
                     if (value == MP_OBJ_SENTINEL) {
-                        return get_aligned(val_type, self->addr, index);
+                        return get_aligned(val_type, struct_addr(self), index);
                     } else {
-                        set_aligned(val_type, self->addr, index, value);
+                        set_aligned(val_type, struct_addr(self), index, value);
                         return value; // just !MP_OBJ_NULL
                     }
                 } else {
-                    byte *p = self->addr + uctypes_struct_scalar_size(val_type) * index;
+                    byte *p = struct_addr(self) + uctypes_struct_scalar_size(val_type) * index;
                     if (value == MP_OBJ_SENTINEL) {
                         return get_unaligned(val_type, p, self->flags);
                     } else {
@@ -657,14 +669,14 @@ mp_obj_t uctypes_struct_subscr(mp_obj_t self_in, mp_obj_t index_in, mp_obj_t val
             } else if (value == MP_OBJ_SENTINEL) {
                 mp_uint_t dummy = 0;
                 mp_uint_t size = uctypes_struct_size(t->items[2], self->flags, &dummy);
-                mp_obj_t args[] = { mp_obj_new_int((mp_uint_t)(uintptr_t)self->addr + size * index), t->items[2], mp_obj_new_int(self->flags) };
+                mp_obj_t args[] = { mp_obj_new_int((mp_uint_t)(uintptr_t)struct_addr(self) + size * index), t->items[2], mp_obj_new_int(self->flags) };
                 return uctypes_struct_make_new(&uctypes_struct_type, MP_ARRAY_SIZE(args), 0, args);
             } else {
                 return MP_OBJ_NULL; // op not supported
             }
 
         } else if (agg_type == PTR) {
-            byte *p = *(void **)self->addr;
+            byte *p = *(void **)struct_addr(self);
             if (mp_obj_is_small_int(t->items[1])) {
                 uint val_type = GET_TYPE(MP_OBJ_SMALL_INT_VALUE(t->items[1]), VAL_TYPE_BITS);
                 if (value == MP_OBJ_SENTINEL) {
@@ -695,7 +707,7 @@ mp_obj_t uctypes_struct_unary_op(mp_unary_op_t op, mp_obj_t self_in) {
                 mp_int_t offset = MP_OBJ_SMALL_INT_VALUE(t->items[0]);
                 uint agg_type = GET_TYPE(offset, AGG_TYPE_BITS);
                 if (agg_type == PTR) {
-                    byte *p = *(void **)self->addr;
+                    byte *p = *(void **)struct_addr(self);
                     return mp_obj_new_int_from_uint((uintptr_t)p);
                 }
             }
@@ -712,9 +724,13 @@ mp_int_t uctypes_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint
     mp_uint_t max_field_size = 0;
     mp_uint_t size = uctypes_struct_size(self->desc, self->flags, &max_field_size);
 
-    bufinfo->buf = self->addr;
+    bufinfo->buf = struct_addr(self);
     bufinfo->len = size;
     bufinfo->typecode = BYTEARRAY_TYPECODE;
+    if (flags & MP_BUFFER_GET_BASE) {
+        bufinfo->base = (void *)self->ptrbase;
+    }
+
     return 0;
 }
 
diff --git a/extmod/vfs_rom_file.c b/extmod/vfs_rom_file.c
index 57aca8c5dc7d3..0811e0f9b1cab 100644
--- a/extmod/vfs_rom_file.c
+++ b/extmod/vfs_rom_file.c
@@ -82,7 +82,7 @@ mp_obj_t mp_vfs_rom_file_open(mp_obj_t self_in, mp_obj_t path_in, mp_obj_t mode_
 
 static mp_int_t vfs_rom_file_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
     mp_obj_vfs_rom_file_t *self = MP_OBJ_TO_PTR(self_in);
-    if (flags == MP_BUFFER_READ) {
+    if ((flags & MP_BUFFER_RW) == MP_BUFFER_READ) {
         bufinfo->buf = (void *)self->file_data;
         bufinfo->len = self->file_size;
         bufinfo->typecode = 'B';
diff --git a/ports/alif/alif_flash.c b/ports/alif/alif_flash.c
index 722afadae1f7b..ddc1668953ca9 100644
--- a/ports/alif/alif_flash.c
+++ b/ports/alif/alif_flash.c
@@ -82,7 +82,7 @@ static mp_obj_t alif_flash_make_new(const mp_obj_type_t *type, size_t n_args, si
 
 static mp_int_t alif_flash_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
     alif_flash_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    if (flags == MP_BUFFER_READ) {
+    if ((flags & MP_BUFFER_RW) == MP_BUFFER_READ) {
         bufinfo->buf = (void *)(ospi_flash_get_xip_base() + self->flash_base_addr);
         bufinfo->len = self->flash_size;
         bufinfo->typecode = 'B';
diff --git a/ports/esp32/esp32_partition.c b/ports/esp32/esp32_partition.c
index f33e9da671b8c..f5184f79323ca 100644
--- a/ports/esp32/esp32_partition.c
+++ b/ports/esp32/esp32_partition.c
@@ -131,7 +131,7 @@ static mp_obj_t esp32_partition_make_new(const mp_obj_type_t *type, size_t n_arg
 #if MICROPY_VFS_ROM_IOCTL
 static mp_int_t esp32_partition_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
     esp32_partition_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    if (self == &esp32_partition_romfs_obj && flags == MP_BUFFER_READ) {
+    if (self == &esp32_partition_romfs_obj && (flags & MP_BUFFER_RW) == MP_BUFFER_READ) {
         if (esp32_partition_romfs_ptr == NULL) {
             check_esp_err(esp_partition_mmap(self->part, 0, self->part->size, ESP_PARTITION_MMAP_DATA, &esp32_partition_romfs_ptr, &esp32_partition_romfs_handle));
         }
diff --git a/ports/rp2/rp2_flash.c b/ports/rp2/rp2_flash.c
index d6b9e13653315..cba6df4fa767d 100644
--- a/ports/rp2/rp2_flash.c
+++ b/ports/rp2/rp2_flash.c
@@ -232,7 +232,7 @@ static mp_obj_t rp2_flash_make_new(const mp_obj_type_t *type, size_t n_args, siz
 
 static mp_int_t rp2_flash_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
     rp2_flash_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    if (flags == MP_BUFFER_READ) {
+    if ((flags & MP_BUFFER_RW) == MP_BUFFER_READ) {
         bufinfo->buf = (void *)(XIP_BASE + self->flash_base);
         bufinfo->len = self->flash_size;
         bufinfo->typecode = 'B';
diff --git a/py/obj.c b/py/obj.c
index 9e7c347b51cb7..f5efe1d320d15 100644
--- a/py/obj.c
+++ b/py/obj.c
@@ -586,8 +586,14 @@ MP_DEFINE_CONST_FUN_OBJ_1(mp_identity_obj, mp_identity);
 
 bool mp_get_buffer(mp_obj_t obj, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
     const mp_obj_type_t *type = mp_obj_get_type(obj);
+    if (flags & MP_BUFFER_GET_BASE) {
+        bufinfo->base = NULL;
+    }
     if (MP_OBJ_TYPE_HAS_SLOT(type, buffer)
-        && MP_OBJ_TYPE_GET_SLOT(type, buffer)(obj, bufinfo, flags & MP_BUFFER_RW) == 0) {
+        && MP_OBJ_TYPE_GET_SLOT(type, buffer)(obj, bufinfo, flags & ~MP_BUFFER_RAISE_IF_UNSUPPORTED) == 0) {
+        if ((flags & MP_BUFFER_GET_BASE) && !bufinfo->base) {
+            bufinfo->base = bufinfo->buf;
+        }
         return true;
     }
     if (flags & MP_BUFFER_RAISE_IF_UNSUPPORTED) {
diff --git a/py/obj.h b/py/obj.h
index 0f87282a9f40b..5239f1a26c262 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -608,12 +608,14 @@ typedef struct _mp_buffer_info_t {
     void *buf;      // can be NULL if len == 0
     size_t len;     // in bytes
     int typecode;   // as per binary.h
+    void *base;     // the "base address" of the buffer, only populated if MP_BUFFER_GET_BASE flag is set and the type supports it.
 } mp_buffer_info_t;
 
 #define MP_BUFFER_READ  (1)
 #define MP_BUFFER_WRITE (2)
 #define MP_BUFFER_RW (MP_BUFFER_READ | MP_BUFFER_WRITE)
 #define MP_BUFFER_RAISE_IF_UNSUPPORTED (4)
+#define MP_BUFFER_GET_BASE (8) // populate the "base" pointer
 
 typedef mp_int_t (*mp_buffer_fun_t)(mp_obj_t obj, mp_buffer_info_t *bufinfo, mp_uint_t flags);
 
diff --git a/py/objarray.c b/py/objarray.c
index bff93088fc8ac..db812b00671ca 100644
--- a/py/objarray.c
+++ b/py/objarray.c
@@ -225,7 +225,7 @@ static mp_obj_t memoryview_make_new(const mp_obj_type_t *type_in, size_t n_args,
     mp_arg_check_num(n_args, n_kw, 1, 1, false);
 
     mp_buffer_info_t bufinfo;
-    mp_get_buffer_raise(args[0], &bufinfo, MP_BUFFER_READ);
+    mp_get_buffer_raise(args[0], &bufinfo, MP_BUFFER_READ | MP_BUFFER_GET_BASE);
 
     mp_obj_array_t *self = MP_OBJ_TO_PTR(mp_obj_new_memoryview(bufinfo.typecode,
         bufinfo.len / mp_binary_get_size('@', bufinfo.typecode, NULL),
@@ -233,12 +233,8 @@ static mp_obj_t memoryview_make_new(const mp_obj_type_t *type_in, size_t n_args,
 
     // If the input object is a memoryview then need to point the items of the
     // new memoryview to the start of the buffer so the GC can trace it.
-    if (mp_obj_get_type(args[0]) == &mp_type_memoryview) {
-        mp_obj_array_t *other = MP_OBJ_TO_PTR(args[0]);
-        self->memview_offset = other->memview_offset;
-        self->items = other->items;
-    }
-
+    self->memview_offset = (char *)bufinfo.buf - (char *)bufinfo.base;
+    self->items = bufinfo.base;
     // test if the object can be written to
     if (mp_get_buffer(args[0], &bufinfo, MP_BUFFER_RW)) {
         self->typecode |= MP_OBJ_ARRAY_TYPECODE_FLAG_RW; // indicate writable buffer
@@ -599,6 +595,9 @@ static mp_int_t array_get_buffer(mp_obj_t o_in, mp_buffer_info_t *bufinfo, mp_ui
             return 1;
         }
         bufinfo->buf = (uint8_t *)bufinfo->buf + (size_t)o->memview_offset * sz;
+        if (flags & MP_BUFFER_GET_BASE) {
+            bufinfo->base = (uint8_t *)o->items;
+        }
     }
     #else
     (void)flags;
diff --git a/py/objringio.c b/py/objringio.c
index ba1ec25307ea4..d89bcc6daf543 100644
--- a/py/objringio.c
+++ b/py/objringio.c
@@ -40,7 +40,7 @@ typedef struct _micropython_ringio_obj_t {
 static mp_obj_t micropython_ringio_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     mp_arg_check_num(n_args, n_kw, 1, 1, false);
     mp_int_t buff_size = -1;
-    mp_buffer_info_t bufinfo = {NULL, 0, 0};
+    mp_buffer_info_t bufinfo = {NULL, 0, 0, 0};
 
     if (!mp_get_buffer(args[0], &bufinfo, MP_BUFFER_RW)) {
         buff_size = mp_obj_get_int(args[0]);
diff --git a/py/objstr.c b/py/objstr.c
index c81fc682fd4e8..6f1ebbdd1fa32 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -2060,7 +2060,7 @@ static MP_DEFINE_CONST_CLASSMETHOD_OBJ(bytes_fromhex_classmethod_obj, MP_ROM_PTR
 #endif // MICROPY_PY_BUILTINS_BYTES_HEX
 
 mp_int_t mp_obj_str_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
-    if (flags == MP_BUFFER_READ) {
+    if ((flags & MP_BUFFER_RW) == MP_BUFFER_READ) {
         GET_STR_DATA_LEN(self_in, str_data, str_len);
         bufinfo->buf = (void *)str_data;
         bufinfo->len = str_len;