MSC: callback order

[mastupristi]

Hi,
I refer to commit 053e37080., and examples host/msc_file_explorer or host/cdc_msc_hid.
In both examples the following callback are defined:

• void tuh_mount_cb(uint8_t dev_addr)
• void tuh_umount_cb(uint8_t dev_addr)
• void tuh_msc_mount_cb(uint8_t dev_addr)
• void tuh_msc_umount_cb(uint8_t dev_addr)

when I insert and then remove an usb pen drive I see:

         <---- insertion
A MassStorage device is mounted
tuh_mount_cb

        ------> extraction
tuh_umount_cb
A MassStorage device is unmounted

I would have expected the reverse order. In other words, first I am notified that there is a mass storage device, and then that a generic device has been inserted?

And then another question: since the two callbacks are differentiated, I imagine it is because they can notify different events. So is it possible that only one of the two callbacks is called at umount? For example, in what scenario could tuh_msc_umount_cb be called but not tuh_umount_cb?