regression in sdram capture on EOS 2000d

[msmeissn]

Describe the bug

Canon EOS 2000D can not do SDRAM capture anymore. Reports PTP device busy.

Name the camera

Canon EOS 2000D

libgphoto2 and gphoto2 version

2.5.31.1 git

To Reproduce

[msmeissn]

bisects to 6a1a3fa672e25c522de13ad24ea6a39546affaa0 is the first bad commit

commit 6a1a3fa672e25c522de13ad24ea6a39546affaa0 Author: axxel awagger@gmail.com Date: Tue Oct 22 11:59:30 2024 +0200

ptp2: cleanup of find_child() and [folder|file]_list_func() functions

Those 3 functions were calling ptp_list_folder to update the object cache
and then iterating over the object cache to find the children of some
specific handle, thereby calling ptp_object_want() which could potentially
remove objects from the list they were iterating over. This was explicitly
marked as "DANGEROUS", which it was.

This patch introduces a return parameter to ptp_list_folder, to let the
caller know, which handles it found. This does two things: a) it is a
potential performance improvement and b) the caller can iterate over a
fixed list of handles, instead of a potentially changing list of objects.
This also did away with the 'retry' logic that tried to deal with this
situation.

I further removed the special fetching of the root folder entries from
the camera_init function and other places and I removed the code
duplication between file_list_func and folder_list_func.

[msmeissn]

hmm, does not happen al the time, so bisect is mood

[msmeissn]

another bisect also kind of found commit 6a1a3fa672e25c522de13ad24ea6a39546affaa0