spi: Convert to PD API version 3

Have edges detected in common library code. Move the test for presence
of optional channels out of the decode loop. Do inspect the very first
sample for pixel compatibility with the previous implementation.

1 files changed, 24 insertions, 22 deletions

diff --git a/decoders/spi/pd.py b/decoders/spi/pd.py
index 4c5aa05..1252a6a 100644
--- a/decoders/spi/pd.py
+++ b/decoders/spi/pd.py
@@ -77,7 +77,7 @@ class ChannelError(Exception):
     pass
 
 class Decoder(srd.Decoder):
-    api_version = 2
+    api_version = 3
     id = 'spi'
     name = 'SPI'
     longname = 'Serial Peripheral Interface'
@@ -137,9 +137,7 @@ class Decoder(srd.Decoder):
         self.ss_transfer = -1
         self.cs_was_deasserted = False
         self.oldcs = None
-        self.oldpins = None
         self.have_cs = self.have_miso = self.have_mosi = None
-        self.no_cs_notification = False
 
     def metadata(self, key, value):
         if key == srd.SRD_CONF_SAMPLERATE:
@@ -307,27 +305,31 @@ class Decoder(srd.Decoder):
         # Found the correct clock edge, now get the SPI bit(s).
         self.handle_bit(miso, mosi, clk, cs)
 
-    def decode(self, ss, es, data):
+    def decode(self):
         if not self.samplerate:
             raise SamplerateError('Cannot decode without samplerate.')
-        # Either MISO or MOSI can be omitted (but not both). CS# is optional.
-        for (self.samplenum, pins) in data:
 
+        # Either MISO or MOSI can be omitted (but not both). CS# is optional.
+        self.have_miso = self.has_channel(1)
+        self.have_mosi = self.has_channel(2)
+        self.have_cs = self.has_channel(3)
+        if not self.have_miso and not self.have_mosi:
+            raise ChannelError('Either MISO or MOSI (or both) pins required.')
+
+        # Tell stacked decoders that we don't have a CS# signal.
+        if not self.have_cs:
+            self.put(0, 0, self.out_python, ['CS-CHANGE', None, None])
+
+        # "Pixel compatibility" with the v2 implementation. Grab and
+        # process the very first sample before checking for edges. The
+        # previous implementation did this by seeding old values with None,
+        # which led to an immediate "change" in comparison.
+        pins = self.wait({})
+        (clk, miso, mosi, cs) = pins
+        self.find_clk_edge(miso, mosi, clk, cs)
+
+        while True:
             # Ignore identical samples early on (for performance reasons).
-            if self.oldpins == pins:
-                continue
-            self.oldpins, (clk, miso, mosi, cs) = pins, pins
-            self.have_miso = (miso in (0, 1))
-            self.have_mosi = (mosi in (0, 1))
-            self.have_cs = (cs in (0, 1))
-
-            # Either MISO or MOSI (but not both) can be omitted.
-            if not (self.have_miso or self.have_mosi):
-                raise ChannelError('Either MISO or MOSI (or both) pins required.')
-
-            # Tell stacked decoders that we don't have a CS# signal.
-            if not self.no_cs_notification and not self.have_cs:
-                self.put(0, 0, self.out_python, ['CS-CHANGE', None, None])
-                self.no_cs_notification = True
-
+            pins = self.wait([{0: 'e'}, {1: 'e'}, {2: 'e'}, {3: 'e'}])
+            (clk, miso, mosi, cs) = pins
             self.find_clk_edge(miso, mosi, clk, cs)