[PATCH] bsg: deprecate BIDI support in bsg

[PATCH] bsg: deprecate BIDI support in bsg

[Christoph Hellwig]

Besides the OSD command set that never got traction, the only SCSI
command using bidirectional buffers is XDWRITEREAD in the 10 and 32
byte variants, which is extremely esoteric.  It probably doesn't make
sense to keep the support code around just for that, so start
deprecating the support.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/bsg.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/bsg.c b/block/bsg.c
index 9a442c23a715..60b41bf79e16 100644
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -177,6 +177,10 @@ bsg_map_hdr(struct request_queue *q, struct sg_io_v4 *hdr, fmode_t mode)
 			goto out;
 		}
 
+		pr_warn_once(
+			"BIDI support in bsg has been deprecated and might be removed. "
+			"Please report your use case to linux-scsi@vger.kernel.org\n");
+
 		next_rq = blk_get_request(q, REQ_OP_SCSI_IN, 0);
 		if (IS_ERR(next_rq)) {
 			ret = PTR_ERR(next_rq);
-- 
2.19.2

Re: [PATCH] bsg: deprecate BIDI support in bsg

[Bart Van Assche]

On Wed, 2018-12-19 at 15:39 +0100, Christoph Hellwig wrote:
> Besides the OSD command set that never got traction, the only SCSI
> command using bidirectional buffers is XDWRITEREAD in the 10 and 32
> byte variants, which is extremely esoteric.  It probably doesn't make
> sense to keep the support code around just for that, so start
> deprecating the support.

You may want to add to the patch description that the XDWRITEREAD command
has been removed from the latest version of SBC-4 (SBC4r15).

Bart.

Re: [PATCH] bsg: deprecate BIDI support in bsg

[Jens Axboe]

On 12/19/18 7:39 AM, Christoph Hellwig wrote:
> Besides the OSD command set that never got traction, the only SCSI
> command using bidirectional buffers is XDWRITEREAD in the 10 and 32
> byte variants, which is extremely esoteric.  It probably doesn't make
> sense to keep the support code around just for that, so start
> deprecating the support.

Acked-by: Jens Axboe <axboe@kernel.dk>

-- 
Jens Axboe

Re: [PATCH] bsg: deprecate BIDI support in bsg

[Christoph Hellwig]

On Wed, Dec 19, 2018 at 03:07:11PM -0800, Bart Van Assche wrote:
> On Wed, 2018-12-19 at 15:39 +0100, Christoph Hellwig wrote:
> > Besides the OSD command set that never got traction, the only SCSI
> > command using bidirectional buffers is XDWRITEREAD in the 10 and 32
> > byte variants, which is extremely esoteric.  It probably doesn't make
> > sense to keep the support code around just for that, so start
> > deprecating the support.
> 
> You may want to add to the patch description that the XDWRITEREAD command
> has been removed from the latest version of SBC-4 (SBC4r15).

Oh, I didn't even noticed that, thanks!

Re: [PATCH] bsg: deprecate BIDI support in bsg

[Christoph Hellwig]

On Wed, Dec 19, 2018 at 04:23:14PM -0700, Jens Axboe wrote:
> On 12/19/18 7:39 AM, Christoph Hellwig wrote:
> > Besides the OSD command set that never got traction, the only SCSI
> > command using bidirectional buffers is XDWRITEREAD in the 10 and 32
> > byte variants, which is extremely esoteric.  It probably doesn't make
> > sense to keep the support code around just for that, so start
> > deprecating the support.
> 
> Acked-by: Jens Axboe <axboe@kernel.dk>

You are the bsg maintainer, so I expected you to pick it up :)

Re: [PATCH] bsg: deprecate BIDI support in bsg

[Jens Axboe]

On 12/20/18 12:12 AM, Christoph Hellwig wrote:
> On Wed, Dec 19, 2018 at 04:23:14PM -0700, Jens Axboe wrote:
>> On 12/19/18 7:39 AM, Christoph Hellwig wrote:
>>> Besides the OSD command set that never got traction, the only SCSI
>>> command using bidirectional buffers is XDWRITEREAD in the 10 and 32
>>> byte variants, which is extremely esoteric.  It probably doesn't make
>>> sense to keep the support code around just for that, so start
>>> deprecating the support.
>>
>> Acked-by: Jens Axboe <axboe@kernel.dk>
> 
> You are the bsg maintainer, so I expected you to pick it up :)

OK - did you to amend the commit message to reflect the death of
XDWRITEREAD as well?

-- 
Jens Axboe

Re: [PATCH] bsg: deprecate BIDI support in bsg

[Douglas Gilbert]

On 2018-12-20 12:09 p.m., Jens Axboe wrote:
> On 12/20/18 12:12 AM, Christoph Hellwig wrote:
>> On Wed, Dec 19, 2018 at 04:23:14PM -0700, Jens Axboe wrote:
>>> On 12/19/18 7:39 AM, Christoph Hellwig wrote:
>>>> Besides the OSD command set that never got traction, the only SCSI
>>>> command using bidirectional buffers is XDWRITEREAD in the 10 and 32
>>>> byte variants, which is extremely esoteric.  It probably doesn't make
>>>> sense to keep the support code around just for that, so start
>>>> deprecating the support.
>>>
>>> Acked-by: Jens Axboe <axboe@kernel.dk>
>>
>> You are the bsg maintainer, so I expected you to pick it up :)
> 
> OK - did you to amend the commit message to reflect the death of
> XDWRITEREAD as well?
> 
It was made obsolete in _draft_ sbc4r15.pdf according to my notes.

It is not "dead", not until SBC-4 is ratified. Until then, SBC-3 is the
current SCSI "block" device standard and it is there as a non-mandatory
command.

Doug Gilbert