CHDK camera_info structure

andrew.stephens.754365

461

« on: 25 / March / 2020, 11:27:17 »

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With a little downtime I decided to try to go a bit deeper into how CHDK works.

Structures are normally defined in a header file and subsequently a function
fills-in the fields.

For some reason, camera_info structure is different. It is defined in camera_info.h as a structure of type _cam_info and that is defined immediately proceeding.

No function fills-in the fields, instead camera_info.c effectively does this
and is added to the compilation.

Why is it done this way and how is it made visible to the rest of the code ?

I have been trying to understand the complex arrangement of makefiles, which
ones are applied to folder 'core' ?

Logged

waterwingz

12140

Re: CHDK camera_info structure

« Reply #1 on: 25 / March / 2020, 13:08:50 »

Quote from: andrew.stephens.754365 on 25 / March / 2020, 11:27:17

Structures are normally defined in a header file and subsequently a function fills-in the fields.

You missed a step. A structure is just a definition of how data is arranged in a section of memory. A map if you like. Something needs to allocate storage space and then the code can save & retrieve information formatted per the structure definition.

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For some reason, camera_info structure is different. It is defined in camera_info.h as a structure of type _cam_info and that is defined immediately proceeding.

That just tells you that the memory starting at location camera_info is organized according to the definition (map) described by _cam_info. The actual memory is allocated (create) and initialzied in the camera_info.c file

Code: [Select]

~line 118 : _cam_info camera_info=

Quote