I was trying to do some USB OTG programming. However it looks like not all relevant registers are exposed in this crate, or at least they are mislabelled, owing to some dodgy SVD files. For instance, FS_DIEPTXF0 appears to be missing from the crate but it looks like it might appear under the name FS_GNPTXFSIZ. This might not be the only inconsistency, if I come across any more I'll report them here as well.

Reading the STM32F446xx reference manual I'd expect FS_DIEPTXF0 to appear in the otg_fs_device module, and FS_HNPTXFSIZ in otg_fs_host. That they have the same offset in the OTG register block and its usage merely depends on the mode in which the core operates - device or host - is a question left to the designers of that peripheral.