pyfastservo: transfer common functions to common

fast-servo/pyfastservo/common.py

@@ -17,6 +17,9 @@
 # You should have received a copy of the GNU General Public License
 # along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+import os
+import mmap
+
 CSR_SIZE = 0x800
 MAP_SIZE = 0x1000
 MAP_MASK = 0xFFF
@@ -71,4 +74,47 @@ CTRL_ADDR               =   DAC_BASE_ADDR + CTRL_OFFSET
 CH0_HIGH_WORD_ADDR      =   DAC_BASE_ADDR + CH0_HIGH_WORD_OFFSET
 CH0_LOW_WORD_ADDR       =   DAC_BASE_ADDR + CH0_LOW_WORD_OFFSET
 CH1_HIGH_WORD_ADDR      =   DAC_BASE_ADDR + CH1_HIGH_WORD_OFFSET
-CH1_LOW_WORD_ADDR       =   DAC_BASE_ADDR + CH1_LOW_WORD_OFFSET
+CH1_LOW_WORD_ADDR       =   DAC_BASE_ADDR + CH1_LOW_WORD_OFFSET
+
+
+def read_from_memory(address, n_bytes):
+    assert n_bytes <= 4
+    addr = address
+
+    try:
+        f = os.open("/dev/mem", os.O_SYNC | os.O_RDWR)
+        with mmap.mmap(
+            f,
+            PAGESIZE,
+            mmap.MAP_SHARED,
+            mmap.PROT_READ | mmap.PROT_WRITE,
+            offset=addr & ~MAP_MASK,
+        ) as mem:
+            start_addr = addr & MAP_MASK
+            stop_addr = start_addr + 4
+            contents = mem[start_addr:stop_addr]
+            read_value = list(contents)[:n_bytes]
+    finally:
+        os.close(f)
+
+    return read_value
+
+def write_to_memory(address, value):
+    value_bytes = value.to_bytes(4, "little")
+    addr = address
+
+    try:
+        f = os.open("/dev/mem", os.O_SYNC | os.O_RDWR)
+        with mmap.mmap(
+            f,
+            PAGESIZE,
+            mmap.MAP_SHARED,
+            mmap.PROT_READ | mmap.PROT_WRITE,
+            offset=addr & ~MAP_MASK,
+        ) as mem:
+            start_addr = addr & MAP_MASK
+            stop_addr = start_addr + 4
+            mem[start_addr:stop_addr] = value_bytes
+            contents = mem[start_addr:stop_addr]
+    finally:
+        os.close(f)