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path: root/Documentation/target/tcmu-design.txt
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2016-03-10target/user: Report capability of handling out-of-order completions to userspaceSheng Yang1-1/+10
TCMU_MAILBOX_FLAG_CAP_OOOC was introduced, and userspace can check the flag for out-of-order completion capability support. Also update the document on how to use the feature. Signed-off-by: Sheng Yang <sheng@yasker.org> Reviewed-by: Andy Grover <agrover@redhat.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
2015-05-30target/user: Add support for bidirectional commandsIlias Tsitsimpis1-1/+1
Enable TCMU to handle bidirectional SCSI commands. In such cases, entries in iov[] cover both the Data-In and the Data-Out buffers. The first iov_cnt entries correspond to the Data-Out buffer, while the remaining iov_bidi_cnt entries correspond to the Data-In buffer. Signed-off-by: Ilias Tsitsimpis <iliastsi@arrikto.com> Signed-off-by: Vangelis Koukis <vkoukis@arrikto.com> Reviewed-by: Andy Grover <agrover@redhat.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
2015-05-30target/user: Only support full command pass-throughAndy Grover1-20/+1
After much discussion, give up on only passing a subset of SCSI commands to userspace and pass them all. Based on what pscsi is doing, make sure to set SCF_SCSI_DATA_CDB for I/O ops, and define attributes identical to pscsi. Make hw_block_size configurable via dev param. Remove mention of command filtering from tcmu-design.txt. Signed-off-by: Andy Grover <agrover@redhat.com> Reviewed-by: Ilias Tsitsimpis <iliastsi@arrikto.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
2015-05-30target/user: Update example code for new ABI requirementsAndy Grover1-2/+6
We now require that the userspace handler set a bit if the command is not handled. Update calls to tcmu_hdr_get_op for v2. Signed-off-by: Andy Grover <agrover@redhat.com> Reviewed-by: Ilias Tsitsimpis <iliastsi@arrikto.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
2015-05-02target/user: Disallow full passthrough (pass_level=0)Andy Grover1-11/+7
TCMU requires more work to correctly handle both user handlers that want all SCSI commands (pass_level=0) for a se_device, and also handlers that just want I/O commands and let the others be emulated by the kernel (pass_level=1). Only support the latter for now. For full passthrough, we will need to support a second se_subsystem_api template, due to configfs attributes being different between the two modes. Thus pass_level is extraneous, and we can remove it. The ABI break for TCMU v2 is already applied for this release, so it's best to do this now to avoid another ABI break in the future. Signed-off-by: Andy Grover <agrover@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
2015-04-19target: Version 2 of TCMU ABIAndy Grover1-15/+28
The initial version of TCMU (in 3.18) does not properly handle bidirectional SCSI commands -- those with both an in and out buffer. In looking to fix this it also became clear that TCMU's support for adding new types of entries (opcodes) to the command ring was broken. We need to fix this now, so that future issues can be handled properly by adding new opcodes. We make the most of this ABI break by enabling bidi cmd handling within TCMP_OP_CMD opcode. Add an iov_bidi_cnt field to tcmu_cmd_entry.req. This enables TCMU to describe bidi commands, but further kernel work is needed for full bidi support. Enlarge tcmu_cmd_entry_hdr by 32 bits by pulling in cmd_id and __pad1. Turn __pad1 into two 8 bit flags fields, for kernel-set and userspace-set flags, "kflags" and "uflags" respectively. Update version fields so userspace can tell the interface is changed. Update tcmu-design.txt with details of how new stuff works: - Specify an additional requirement for userspace to set UNKNOWN_OP (bit 0) in hdr.uflags for unknown/unhandled opcodes. - Define how Data-In and Data-Out fields are described in req.iov[] Changed in v2: - Change name of SKIPPED bit to UNKNOWN bit - PAD op does not set the bit any more - Change len_op helper functions to take just len_op, not the whole struct - Change version to 2 in missed spots, and use defines - Add 16 unused bytes to cmd_entry.req, in case additional SAM cmd parameters need to be included - Add iov_dif_cnt field to specify buffers used for DIF info in iov[] - Rearrange fields to naturally align cdb_off - Handle if userspace sets UNKNOWN_OP by indicating failure of the cmd - Wrap some overly long UPDATE_HEAD lines (Add missing req.iov_bidi_cnt + req.iov_dif_cnt zeroing - Ilias) Signed-off-by: Andy Grover <agrover@redhat.com> Reviewed-by: Ilias Tsitsimpis <iliastsi@arrikto.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
2014-10-02target: Add documentation on the target userspace pass-through driverAndy Grover1-0/+378
Describes the driver and its interface to make it possible for user programs to back a LIO-exported LUN. Thanks to Richard W. M. Jones for review, and supplementing this doc with the first two paragraphs. Signed-off-by: Andy Grover <agrover@redhat.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>