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The gphoto2 device database (gp2ddb)
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Important: This is a prototype the developers can play with. The final
version will look much different, so don't invest too much
in it.
Note: We try to talk of "devices" and "drivers" instead of "cameras"
and "camlibs" since we also support digital audio players.
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The idea
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* Maintain a device database (DDB) of cameras (and audio players),
their abilities etc. independently from the libgphoto2 camlibs.
* Updates to the database are much easier to publish than updates to
the camlibs which need to be compiled.
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The implementation
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* A flex/bison based parser for text based config.
* The text format is not completely ironed out yet.
* It is possible to use some HAL device database instead, but do we
really want to require HAL? Depends whether we target embedded or
desktop environments.
* print-camera-list prints the current config in the new format
(minus camlib internal settings)
* camlib specific settings can be accommodated using the
driver_options { ... }; section.
* The binary code (stripped) for the test case is about 22KByte. I
suppose we could implement this database in about 35 to 40 KByte.
However, we can probably get rid of some code in the drivers to
compensate.
For comparison:
* The current libgphoto2.so is about 120 KByte stripped.
* libxml2.so is 1.2MB (stripped).
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The testcase
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* The testcase check-ddb.sh checks that the CameraAbilitiesList read
from the text database is the same one read from the camlibs via
gp_abilities_list_load() - for all 700something cameras.
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How to test it
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* Add --enable-gp2ddb to your ./configure parameters.
* Run "make check".
* Have a look into tests/ddb/.
* Possibly add the output of
(hostname;cat /proc/cpuinfo)|md5sum|cut -d" " -f1
to the list in configure.in to avoid the --enable-gp2ddb
requirement.
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TODO
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What would need to be done to go into production with this:
* Find a way to integrate the gphoto2 DDB with the HAL device
database, possibly using a sub/superset of the HAL device
database. However, HAL does its stuff in XML, and we probably don't
want libgphoto2 to depend on an XML parser.
* Add driver specific parameters to DDB.
* Rewrite gp_abilities_list_load() to read the data currently stored
in the CameryAbilities record and all driver specific information
from the DDB.
* Rewrite all drivers to read their device specific parameters from
the new CameraAbilities record.
* Maintain binary compatibility.
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End of file.
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