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comm_sg.py
111 lines (103 loc) · 4.18 KB
/
comm_sg.py
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#! /usr/bin/env python
# Module does not require root, merely the SG module to be loaded.
# The Lytro presents itself as a CD-ROM so being in the cdrom group is enough.
# However, this isn't perfectly stable yet; attempting a download (e.g. list pictures)
# sometimes causes the camera to crash and restart. Usually works after that, though.
import glob, posix, fcntl, struct, time
from ctypes import *
import lytro
# Implement Linux SG_IO ioctl
SG_IO = 0x2285
class sg_io_hdr(Structure):
"sg_io_hdr structure, see /usr/include/scsi/sg.h for details"
_fields_ = [
('interface_id', c_int),
('dxfer_direction', c_int),
('cmd_len', c_ubyte),
('mx_sb_len', c_ubyte),
('iovec_count', c_ushort),
('dxfer_len', c_uint),
('dxferp', c_void_p),
('cmdp', c_char_p),
('sbp', POINTER(c_ubyte)),
('timeout', c_uint),
('flags', c_uint),
('pack_id', c_int),
('usr_ptr', c_void_p),
('status', c_ubyte),
('masked_status', c_ubyte),
('msg_status', c_ubyte),
('sb_len_wr', c_ubyte),
('host_status', c_ushort),
('driver_status', c_ushort),
('resid', c_int),
('duration', c_uint),
('info', c_uint),
]
SG_DXFER_NONE = -1
SG_DXFER_TO_DEV = -2
SG_DXFER_FROM_DEV = -3
class sensebuffer(Structure):
"SCSI sense data"
_fields_ = [
('response_code', c_ubyte),
('sense_key', c_ubyte),
('additional_sense_code', c_ubyte),
('additional_sense_qualifier', c_ubyte),
('_reserved0', 3*c_ubyte),
('additional_sense_length', c_ubyte),
# ... sense data descriptors
]
def __str__(self):
return str({a: getattr(self, a) for a in dir(self) if not a.startswith('_')})
class ScsiTarget(lytro.Target):
def __init__(self, name):
if not name.startswith('sg:'):
raise ValueError(f"Not a SG target: {name}")
self.fd = posix.open(name[3:], posix.O_RDWR)
def read(self, command, size):
# Lytro can produce 32KiB per transfer (SG allows 64)
sizelimit = 1<<15
if size > sizelimit:
size = sizelimit
buf = create_string_buffer(size)
for n in range(10):
sb = sensebuffer()
hdr = sg_io_hdr(interface_id=ord('S'), timeout=1000,
cmdp=command, cmd_len=len(command),
mx_sb_len=sizeof(sb), sbp=cast(pointer(sb), POINTER(c_ubyte)),
dxfer_direction=SG_DXFER_FROM_DEV,
dxferp=cast(pointer(buf), c_void_p), dxfer_len=size)
result = fcntl.ioctl(self.fd, SG_IO, hdr)
assert result==0
if sb.response_code==0:
break
time.sleep(0.05)
# FIXME: nothing is read? our buffer seems to hold only nul
# It works fine for the time, battery and size commands
#print(sb)
#print(repr(buf.raw[:16]))
return buf.raw[:size-hdr.resid]
def write(self, command, data):
data = create_string_buffer(data)
sb = sensebuffer()
hdr = sg_io_hdr(interface_id=ord('S'), timeout=1000,
cmdp=command, cmd_len=len(command),
mx_sb_len=0, #sbp=cast(pointer(sb), POINTER(c_ubyte)),
dxfer_direction=SG_DXFER_TO_DEV,
dxferp=cast(pointer(data), c_void_p), dxfer_len=len(data))
fcntl.ioctl(self.fd, SG_IO, hdr)
def probe():
import pathlib
for path in glob.glob('/sys/class/scsi_generic/sg?/device/vendor'):
if open(path).read() == 'Lytro \n':
yield "sg:/dev/"+pathlib.Path(path).parts[-3]
# CD-ROM device works for battery status, but not downloads
#return glob.glob('/dev/disk/by-id/usb-Lytro*')
def test_getbat():
getbat=struct.pack('<HB13x', 0xc6, 6)
for name in probe():
t=ScsiTarget(name)
print("Battery level for %s: %g%%"%(name, struct.unpack('<f',t.read(getbat,4))[0]))
if __name__=='__main__':
test_getbat()