Re: [PATCH v2 0/1] MR7747: ntdll: Guess optical disc type based on data size.

[Jinoh Kang (＠iamahuman)]

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?