On Mon, May 04, 2020 at 10:45:33AM +0200, Stefan Haberland wrote:

quoted

findthe corresponding device for example. Not sure if this is that easy.

I did some additional research on this.
What I could imagine:

The gendisk->private_data pointer currently contains a pointer to
the dasd_devmap structure. This one is also reachable by iterating
over an exported dasd_hashlist.
So I could export the dasd_hashlist symbol, iterate over it and try
to find the dasd_devmap pointer I have from the gendisk->private_data
pointer.
This would ensure that the gendisk belongs to the DASD driver and I
could use the additional information that is somehow reachable through
the gendisk->private_data pointer.

But again, I am not sure if this additional code and effort is needed.
From my point of view checking the gendisk->major for DASD_MAJOR is
OK to ensure that the device belongs to the DASD driver.

With CONFIG_DEBUG_BLOCK_EXT_DEVT you can't rely on major numbers.

And compared to all the complications I think the biodasdinfo method
is the least of all those evils.  Jens, any opinion?