Re: problem with USB-CD drive

> It looks like the device or driver do not like size of reading request,
> f.e. short read. It should be possible to verify that using several ways:
>
> 1) run "ktrace -i mount_cd9660 ..." then study ouput of kdump;


    847 mount_cd9660 STRU  struct stat {dev=156, ino=261120, mode=040755, 
nlink=2, uid=0, gid=0, rdev=2085752, atime=1581328619, mtime=15
81328630.081523000, ctime=1581328648.345917000, birthtime=315532800, 
size=1024, blksize=32768, blocks=8, flags=0x0 }
    847 mount_cd9660 RET   lstat 0
    847 mount_cd9660 CALL  stat(0x7fffffffe440,0x7fffffffe3a0)
    847 mount_cd9660 NAMI  "/mnt"
    847 mount_cd9660 STRU  struct stat {dev=156, ino=261120, mode=040755, 
nlink=2, uid=0, gid=0, rdev=2085752, atime=1581328619, mtime=15
81328630.081523000, ctime=1581328648.345917000, birthtime=315532800, 
size=1024, blksize=32768, blocks=8, flags=0x0 }
    847 mount_cd9660 RET   stat 0
    847 mount_cd9660 CALL  openat(AT_FDCWD,0x7fffffffee6d,0<O_RDONLY>)
    847 mount_cd9660 NAMI  "/dev/cd1"
    847 mount_cd9660 RET   openat 3
    847 mount_cd9660 CALL  ioctl(0x3,CDIOREADTOCHEADER,0x7fffffffeb88)
    847 mount_cd9660 RET   ioctl 0
    847 mount_cd9660 CALL  ioctl(0x3,CDIOREADTOCENTRYS,0x7fffffffeb60)
    847 mount_cd9660 RET   ioctl 0
    847 mount_cd9660 CALL  close(0x3)
    847 mount_cd9660 RET   close 0
    847 mount_cd9660 CALL 
mmap(0,0x200000,0x3<PROT_READ|PROT_WRITE>,0x1002<MAP_PRIVATE|MAP_ANON>,0xffffffff,0)
    847 mount_cd9660 RET   mmap 34376515584/0x801000000
    847 mount_cd9660 CALL  nmount(0x801015080,0x8,0x1<MNT_RDONLY>)
    847 mount_cd9660 NAMI  "/mnt"
    847 mount_cd9660 NAMI  "/mnt"
    847 mount_cd9660 NAMI  "/dev/cd1"
    847 mount_cd9660 RET   nmount -1 errno 22 Invalid argument

could you please help me to understand this?

is it something about CDIOREADTOCHEADER and CDIOREADTOCENTRYS returning 
not what it should return?




> 2) enable debug logs at GEOM level, use sysctl kern.geom.debugflags=255
> (beware of large amount of logs) then run mount_cd9660
> 3) use gcache(8) that is capable of limiting minimum request size by caching "extra" data,
> but try using only single gcache(8) instance per system because of known instability in the gcache code
> when you create multiple geom_cache's.
>
>
did gcache with 2kB blocks. works fine. Seems like a problem is here - 
some requests are not handled.

now i tested reading it with dd with 2,4,8,16 and 32kB blocks. seems fine.

trying to read with blocks like 1k, 512 doesn't work but it is i think 
normal - CDs have 2kB blocks.

real CD drive behaves the same way.