diff options
Diffstat (limited to 'decoders')
| -rw-r--r-- | decoders/i2cfilter/pd.py | 89 |
1 files changed, 51 insertions, 38 deletions
diff --git a/decoders/i2cfilter/pd.py b/decoders/i2cfilter/pd.py index a54baab..877c467 100644 --- a/decoders/i2cfilter/pd.py +++ b/decoders/i2cfilter/pd.py @@ -18,8 +18,12 @@ ## along with this program; if not, see <http://www.gnu.org/licenses/>. ## -# TODO: Support for filtering out multiple slave/direction pairs? +# TODO +# - Accept other slave address forms than decimal numbers? +# - Support for filtering out multiple slave/direction pairs? +# - Support 10bit slave addresses? +import copy import sigrokdecode as srd class Decoder(srd.Decoder): @@ -43,51 +47,60 @@ class Decoder(srd.Decoder): self.reset() def reset(self): - self.curslave = -1 - self.curdirection = None - self.packets = [] # Local cache of I²C packets + self.seen_packets = [] + self.do_forward = None def start(self): self.out_python = self.register(srd.OUTPUT_PYTHON, proto_id='i2c') if self.options['address'] not in range(0, 127 + 1): raise Exception('Invalid slave (must be 0..127).') + self.want_addrs = [] + if self.options['address']: + self.want_addrs.append(self.options['address']) + self.want_dir = { + 'read': 'READ', 'write': 'WRITE', + }.get(self.options['direction'], None) - # Grab I²C packets into a local cache, until an I²C STOP condition - # packet comes along. At some point before that STOP condition, there - # will have been an ADDRESS READ or ADDRESS WRITE which contains the - # I²C address of the slave that the master wants to talk to. - # If that slave shall be filtered, output the cache (all packets from - # START to STOP) as proto 'i2c', otherwise drop it. - def decode(self, ss, es, data): + def _need_to_forward(self, slave_addr, direction): + if self.want_addrs and slave_addr not in self.want_addrs: + return False + if self.want_dir and direction != self.want_dir: + return False + return True - cmd, databyte = data + # Accumulate observed I2C packets until a STOP or REPEATED START + # condition is seen. These are conditions where transfers end or + # where direction potentially changes. Forward all previously + # accumulated traffic if it passes the slave address and direction + # filter. This assumes that the slave address as well as the read + # or write direction was part of the observed traffic. There should + # be no surprise when incomplete traffic does not match the filter + # condition. + def decode(self, ss, es, data): - # Add the I²C packet to our local cache. - self.packets.append([ss, es, data]) + # Unconditionally accumulate every lower layer packet we see. + # Keep deep copies for later, only reference caller's values + # as long as this .decode() invocation executes. + self.seen_packets.append([ss, es, copy.deepcopy(data)]) + cmd, _ = data + # Check the slave address and transfer direction early when + # we see them. Keep accumulating packets while it's already + # known here whether to forward them. This simplifies other + # code paths. Including future handling of 10bit addresses. if cmd in ('ADDRESS READ', 'ADDRESS WRITE'): - self.curslave = databyte - self.curdirection = cmd[8:].lower() - elif cmd in ('STOP', 'START REPEAT'): - # If this chunk was not for the correct slave, drop it. - if self.options['address'] == 0: - pass - elif self.curslave != self.options['address']: - self.packets = [] - return - - # If this chunk was not in the right direction, drop it. - if self.options['direction'] == 'both': - pass - elif self.options['direction'] != self.curdirection: - self.packets = [] - return - - # TODO: START->STOP chunks with both read and write (Repeat START) - # Otherwise, send out the whole chunk of I²C packets. - for p in self.packets: - self.put(p[0], p[1], self.out_python, p[2]) + direction = cmd[len('ADDRESS '):] + _, slave_addr = data + self.do_forward = self._need_to_forward(slave_addr, direction) + return - self.packets = [] - else: - pass # Do nothing, only add the I²C packet to our cache. + # Forward previously accumulated packets as we see their + # completion, and when they pass the filter condition. Prepare + # to handle the next transfer (the next read/write part of it). + if cmd in ('STOP', 'START REPEAT'): + if self.do_forward: + for ss, es, data in self.seen_packets: + self.put(ss, es, self.out_python, data) + self.seen_packets.clear() + self.do_forward = None + return |