[PATCH] Cygwin: Add /dev/disk/by-id symlinks
Christian Franke
Christian.Franke@t-online.de
Sat Nov 4 11:34:04 GMT 2023
Corinna Vinschen wrote:
> On Nov 4 10:34, Corinna Vinschen wrote:
>> On Nov 3 18:54, Christian Franke wrote:
>>> ...
>>>> MSDN claims:
>>>>
>>>> If the storage device is SCSI-compliant, the port driver attempts to
>>>> extract the serial number from the optional Unit Serial Number page
>>>> (page 0x80) of the VPD.
>>>>
>>>> Now I'm puzzled.
>>> A quick test with a Debian 12 VM in VirtualBox with many virtual
>>> controllers+drives shows the same problem:
>>> Entries in /dev/disk/by-id appear only for virtual disks behind emulated
>>> SATA and NVMe controllers, but not for SCSI and SAS controllers.
>>> A test with "smartctl -i ..." with SCSI/SAS devices doesn't print a serial
>>> number. In debug mode it prints "Vital Product Data (VPD) INQUIRY failed..."
>>> and other messages that suggest limited/buggy support of optional SCSI
>>> commands.
>>>
>>> If a Win11 PE (from install ISO) is run in same VM, the
>>> STORAGE_DEVICE_DESCRIPTOR only provides the serial number for SATA (NVMe
>>> drives not detected), but not for SCSI.
>>>
>>> Conclusion: The behavior of the current patch is compatible with Linux :-)
>> Ok, but with the DUID we have a workaround which makes it work even
>> better than on Linux, so it would begreat if we used it, unless we find
>> out where the UUID in "\GLOBAL??\Disk{<UUID>} comes from...
>>
>> Given the size of the STORAGE_DEVICE_UNIQUE_IDENTIFIER struct, we could
>> even contemplate a 128 bit hash, just to be on the safe side.
> Kind of like this
>
> - strcat (name, ioctl_buf + desc->SerialNumberOffset);
> + /* Use SerialNumber in the first place, if available */
> + if (desc->SerialNumberOffset && desc_buf[desc->SerialNumberOffset])
> + strcat (name, desc_buf + desc->SerialNumberOffset);
> + else /* Utilize the DUID as defined by MSDN to generate a hash */
> + {
> + union {
> + unsigned __int128 all;
> + struct {
> + unsigned long high;
> + unsigned long low;
> + };
> + } hash = { 0 };
> +
> + for (ULONG i = 0; i < id->Size; ++i)
> + hash.all = ioctl_buf[i] + (hash.all << 6) + (hash.all << 16) - hash.all;
> + __small_sprintf (name + strlen (name), "%X%X", hash.high, hash.low);
> + }
>
I agree and will provide a new patch soon.
Christian
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