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scsi: ufs: Add a bsg endpoint that supports UPIUs

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For now, just provide an API to allocate and remove ufs-bsg node. We
will use this framework to manage ufs devices by sending UPIU
transactions.

For the time being, implements an empty bsg_request() - will add some
more functionality in coming patches.

Nonetheless, we reveal here the protocol we are planning to use: UFS
Transport Protocol Transactions. UFS transactions consist of packets
called UFS Protocol Information Units (UPIU).

There are UPIU’s defined for UFS SCSI commands, responses, data in and
data out, task management, utility functions, vendor functions,
transaction synchronization and control, and more.

By using UPIUs, we get access to the most fine-grained internals of this
protocol, and able to communicate with the device in ways, that are
sometimes beyond the capacity of the ufs driver.

Moreover and as a result, our core structure - ufs_bsg_node has a pretty
lean structure: using upiu transactions that contains the outmost
detailed info, so we don't really need complex constructs to support it.

Signed-off-by: Avri Altman <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>
This commit is contained in:
Avri Altman 2018-10-07 17:30:35 +03:00 • committed by Martin K. Petersen
commit df032bf27a
8 changed files with 192 additions and 1 deletions
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20
Documentation/scsi/ufs.txt
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@ -128,6 +128,26 @@ The current UFSHCD implementation supports following functionality,
In this version of UFSHCD Query requests and power management
functionality are not implemented.
4. BSG Support
------------------
This transport driver supports exchanging UFS protocol information units
(UPIUs) with a UFS device. Typically, user space will allocate
struct ufs_bsg_request and struct ufs_bsg_reply (see ufs_bsg.h) as
request_upiu and reply_upiu respectively. Filling those UPIUs should
be done in accordance with JEDEC spec UFS2.1 paragraph 10.7.
*Caveat emptor*: The driver makes no further input validations and sends the
UPIU to the device as it is. Open the bsg device in /dev/ufs-bsg and
send SG_IO with the applicable sg_io_v4:
io_hdr_v4.guard = 'Q';
io_hdr_v4.protocol = BSG_PROTOCOL_SCSI;
io_hdr_v4.subprotocol = BSG_SUB_PROTOCOL_SCSI_TRANSPORT;
io_hdr_v4.response = (__u64)reply_upiu;
io_hdr_v4.max_response_len = reply_len;
io_hdr_v4.request_len = request_len;
io_hdr_v4.request = (__u64)request_upiu;
UFS Specifications can be found at,
UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf