I am trying to get EOS M2 supported in libgphoto2. Basically the camera
looks perfectly controllable over USB (better than its descendants),
but some tweaks are needed, and I'd like to discuss them here before
submitting a patch.

First of all, the camera requires regetting device info after setting
the remote mode to 0x15. For this reason currently the shooting related
commands work only every other time: get device info while the remote
mode is still 0 -- set the remote mode to 0x15 -- report caption not
supported -- exit -- get device info, this time with the remote mode
0x15 -- successfully capture an image -- reset the remote mode to 0,
and so on. Of course there is no problem to insert one more
ptp_getdeviceinfo() call into camera_init(), but this doesn't look
optimal, as the function is later called once more from
camera_prepare_canon_eos_capture(). So might it be possible to somehow
minimize the number of those calls?

Second, when accessing the M2 I get multiple error messages:
"halfsize 0 is not expected 278". It seems the camera indeed
produces a useless PTP_DPC_CANON_EOS_FocusInfoEx field, filled
with zeroes. Since this is not actually an error and the message
is quite irritating, I'd like to know if it would be OK to disable it
just for one particular camera.

Also, my previous patch for EOS M non-focus doesn't work here and needs
to be updated. It would be interesting to have a look at logs of other
EOS M* cameras to see if they behave differently at this point.

Alexey Kryukov <anagnost at yandex dot ru>

Moscow State University
Faculty of History

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