[libusb] RFC on upcoming API changes

[Tormod V. <lis...@gm...>]

Dear libusb users, contributors, and friends,

We currently have a good number of pull requests in our tracker at
GitHub, and we hope to merge many of these soon and prepare the next
release 1.0.27. Some of these are API changes, for which special care
and foresight is needed. However we are in a situation were most
senior core libusb developers are "missing in action" or swamped with
other work for a long time. As a relative new libusb contributor
without a good overview on how and why the API has been shaped over
the years I don't feel comfortable merging them without additional
review and comments.

I know there are many experienced developers here on the list that may
not be looking much on our issue/PR tracker or participate there. I
would therefore like to ask here on the list for comments on the
following API changes. The most important, and what I really want
review on, is the API change itself. E.g. Is it a useful change and
something we want to live with on longer term, and the best way to
solve the original problem or shortcomings, does the new function have
the best name? (The implementation in code matters less for this
discussion, it can always be fixed or improved later. Code reviews are
still welcome of course!)

Feel free to comment directly on the GitHub issue, but if you prefer
the mailing list that is very fine too.


[1] #1026 core: Add libusb_init_context to allow setting options
during context creation

The suggested libusb_init_context() should allow a better way to set
options than the current practice of, in some cases, setting options
for the "default context", then creating the context with
libusb_init(). This will probably be the recommended way, although
we'll keep libusb_init() for backwards compatibility for a long time.


[2] #1167 core: Add libusb_get_max_iso_packet_size_for_alt_setting

This was discussed on the list many years ago. It is mostly useful for
isochronous packets but works for all kinds. It should in many cases
be preferred over the existing libusb_get_max_iso_packet_size() which
only considers the currently active alternate setting.


[3] #1208 Add support for enabling or disabling the WinUSB RAW_IO
option on an endpoint

This is a tricky one (and Windows specific) but it seems there is a
good solution.


[4] #1133 descriptor: Add support for BOS platform descriptor parsing

This PR includes a new libusb_get_platform_descriptor() helper
function as a side effect.


Final note, as you can see these are all extensions to the existing
API and not changing any of the existing behaviour.

Looking forward to your comments and thanks for your help,
Tormod


[1] https://github.com/libusb/libusb/pull/1026
[2] https://github.com/libusb/libusb/pull/1167
[3] https://github.com/libusb/libusb/pull/1208
[4] https://github.com/libusb/libusb/pull/1133