py: Fix mp_get_buffer, and use it in more places.

Must use mp_obj_get_type to get the type of an object.  Can't assume
mp_obj_t is castable to mp_obj_base_t.

1 files changed, 1 insertions, 5 deletions

diff --git a/stmhal/dac.c b/stmhal/dac.c
index 22622d474..5e809412e 100644
--- a/stmhal/dac.c
+++ b/stmhal/dac.c
@@ -180,12 +180,8 @@ mp_obj_t pyb_dac_dma(uint n_args, const mp_obj_t *args, mp_map_t *kw_args) {
     // set TIM6 to trigger the DAC at the given frequency
     TIM6_Config(mp_obj_get_int(args[2]));
 
-    mp_obj_type_t *type = mp_obj_get_type(args[1]);
-    if (type->buffer_p.get_buffer == NULL) {
-        nlr_raise(mp_obj_new_exception_msg(&mp_type_TypeError, "buffer argument must support buffer protocol"));
-    }
     buffer_info_t bufinfo;
-    type->buffer_p.get_buffer(args[1], &bufinfo, BUFFER_READ);
+    mp_get_buffer_raise(args[1], &bufinfo);
 
     __DMA1_CLK_ENABLE();