Comment # 22 on bug 1095096 from Johannes Thumshirn

OK I think I know the difference now.

scsi_id (please correct me if I'm worng here Franck) sends different SCSI
pass-though commands to the device.

I've always concentrated on VPD page code 0x83 for the translation, eventually
resulting in nvme_trans_device_id_page() in the nvme scsi compat layer.

But it can also sent a page_code of 0x80 resulting in
nvme_trans_unit_serial_page(). This (nvme_trans_unit_serial_page()) just copies
the first 20 bytes of the controller serial number into the SCSI Inquiry
Response.

OTOH this is corresponds with the value that's in sysfs' serial attribute.