Re: [PATCH 1/1] s390/dasd: remove ioctl_by_bdev from DASD driver

[Christoph Hellwig]

On Thu, May 07, 2020 at 05:22:28PM +0200, Stefan Haberland wrote:
> OK, just thought again about your suggestion and also that
> you have already been talking about a symbol lookup I just
> have written a prototype that took your first two patches
> as base, exports the symbol of dasd_biodasdinfo and in
> ibm.c I do a kallsyms_lookup_name("dasd_biodasdinfo").
> 
> So I would not have to define a structure twice or rely on
> MAJORs. Also we would not have to define an own file
> operation only for DASD devices.
> 
> What do you think about this? If you agree I will polish
> the patches, test them and send them for review.

How do you figure out a given gendisk is a DASD device?  I guess
dasd_biodasdinfo could just check the block_device_operations
pointer first thing.  That's still a little ugly, but seems the
least bad idea so far, so please at least post it for discussion.