On Mon, Sep 07, 2020 at 05:01:34PM +0800, Tom Yan wrote: > Feel free to omit this. But then you will probably want to ditch > BLKSECTGET as well, and then any usage of queue_max_sectors(), and > maybe more/all queue_*(). > > I'm not really interested in discussing/arguing whether > general/ideally-speaking it's appropriate/necessary to keep BLKSECTGET > / add BLKSSZGET. The only reason I added this is that, when BLKSECTGET > was introduced to sg long time ago, it was wrongly implemented to > gives out the limit in bytes, so now when I'm fixing it, I'm merely > making sure that whatever has been relying on the ioctl (e.g. qemu) > will only need to do one more ioctl (instead of e.g. doing SCSI in its > non-SCSI-specific part), if they want/need the limit in bytes. If they > can be implemented more "generic"-ly, feel free to improve/extend them > to make them "SG_*-qualified". > > Even if you can do SCSI from the userspace, or even should, I don't > see any reason that we shouldn't provide an ioctl to do > queue_logical_block_size() *while we provide one to do > queue_max_sectors()*. Well, the different definition in bytes for sg actually makes sense to me, as a bytes based limit is what fundamentally makes sense for the passthrough interface. Only that it reuses the same cmd value is a bit confusing. So instead of changing anything and potentially breaking applications I'd suggest to just better document the semantics.
