On Fri May 23 04:23:45 2025 +0000, Alex Henrie wrote:
Linux has only three [DVD ioctls](https://docs.kernel.org/userspace-api/ioctl/cdrom.html): DVD_READ_STRUCT, DVD_WRITE_STRUCT, and DVD_AUTH. It has no blu-ray ioctls. Of the three DVD ioctls, only DVD_READ_STRUCT would be suitable for disc type detection. DVD_READ_STRUCT can read five kinds of information: DVD_STRUCT_PHYSICAL, DVD_STRUCT_COPYRIGHT, DVD_STRUCT_DISCKEY, DVD_STRUCT_BCA, and DVD_STRUCT_MANUFACT. Of those five, only DVD_STRUCT_PHYSICAL would be suitable for disc type detection. At least on my LG WH16NS40 drive, DVD_STRUCT_PHYSICAL succeeds when there is a DVD in the drive, but it fails when there is a CD or a blu-ray in the drive. That means that we could use DVD_STRUCT_PHYSICAL to accurately detect whether there is a DVD in the drive, but we would still need another way to detect blu-rays. Is there another ioctl that you had in mind, or something else that I missed? Do you want to try DVD_STRUCT_PHYSICAL first and fall back to guessing based on the data size if it fails? Please let me know how to proceed.
Any chance it could be a driver bug?
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Jinoh Kang (＠iamahuman)