From patchwork Tue Dec 15 20:33:20 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bart Van Assche X-Patchwork-Id: 67741 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id nBFKXmOe002227 for ; Tue, 15 Dec 2009 20:33:49 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933174AbZLOUdf (ORCPT ); Tue, 15 Dec 2009 15:33:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933619AbZLOUde (ORCPT ); Tue, 15 Dec 2009 15:33:34 -0500 Received: from jester.euphonynet.be ([212.87.96.13]:39692 "EHLO mailpush2.euphonynet.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933174AbZLOUdc (ORCPT ); Tue, 15 Dec 2009 15:33:32 -0500 Received: from ripley.euphonynet.be (ripley.euphonynet.be [212.87.96.9]) by mailpush2.euphonynet.be (Postfix) with ESMTP id E63F04F84EC; Tue, 15 Dec 2009 21:33:28 +0100 (CET) Received: from localhost (scan03.euphonynet.be [212.87.96.25]) by ripley.euphonynet.be (Postfix) with ESMTP id C8DAEBB2E50E5; Tue, 15 Dec 2009 21:33:28 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at euphonynet.be Received: from smtp2.euphonynet.be ([212.87.96.4]) by localhost (scan03.euphonynet.be [212.87.96.23]) (amavisd-new, port 10024) with ESMTP id B01fdn5Yicz8; Tue, 15 Dec 2009 21:33:21 +0100 (CET) Received: from eu85-10-94-241.localnet (unknown [85.10.77.119]) by smtp2.euphonynet.be (Postfix) with ESMTP id BA64D68074BDF; Tue, 15 Dec 2009 21:33:20 +0100 (CET) From: Bart Van Assche To: linux-scsi@vger.kernel.org, linux-rdma@vger.kernel.org Subject: [PATCH] SCSI/libsrp: document the libsrp source code Date: Tue, 15 Dec 2009 21:33:20 +0100 User-Agent: KMail/1.12.2 (Linux/2.6.30.7-scst; KDE/4.3.1; x86_64; ; ) Cc: "James E.J. Bottomley" , FUJITA Tomonori MIME-Version: 1.0 Message-Id: <200912152133.20204.bart.vanassche@gmail.com> Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org diff --git a/drivers/scsi/libsrp.c b/drivers/scsi/libsrp.c index 9ad38e8..bd3229e 100644 --- a/drivers/scsi/libsrp.c +++ b/drivers/scsi/libsrp.c @@ -29,6 +29,10 @@ #include #include +/* + * Allowed values for the 'TASK ATTRIBUTE' field of an SRP_CMD request. See + * also section 6.8 of the T10 SRP r16a document. + */ enum srp_task_attributes { SRP_SIMPLE_TASK = 0, SRP_HEAD_TASK = 1, @@ -44,6 +48,16 @@ do { \ /* #define dprintk eprintk */ #define dprintk(fmt, args...) +/** + * Allocate a pool of information units for use by an SRP target. + * @q: pointer to the pool structure that will be initialized. + * @max: number of information units the pool will contain. + * @ring: pointer to an array of 'max' SRP buffer pointers. Each information + * unit allocated for the pool will be initialized such that it points to + * the corresponding SRP buffer in array 'ring'. + * + * Returns zero upon success and a negative error code upon failure. + */ static int srp_iu_pool_alloc(struct srp_queue *q, size_t max, struct srp_buf **ring) { @@ -77,12 +91,26 @@ free_pool: return -ENOMEM; } +/** + * Free the memory allocated by srp_iu_pool_alloc(). + * + * Note: the memory occupied by the struct srp_queue itself is not freed + * -- this is the responsibility of the caller. + */ static void srp_iu_pool_free(struct srp_queue *q) { kfree(q->items); kfree(q->pool); } +/** + * Allocate a ring of SRP buffers and set up a coherent DMA mapping for each + * buffer. + * @max: number of elements the ring will contain. + * @size: size in bytes of one ring element. + * + * Returns a pointer to an array of 'max' pointers to SRP buffers. + */ static struct srp_buf **srp_ring_alloc(struct device *dev, size_t max, size_t size) { @@ -115,6 +143,7 @@ out: return NULL; } +/** Free the memory allocated by srp_ring_alloc(). */ static void srp_ring_free(struct device *dev, struct srp_buf **ring, size_t max, size_t size) { @@ -127,6 +156,15 @@ static void srp_ring_free(struct device *dev, struct srp_buf **ring, size_t max, kfree(ring); } +/** + * Initialize an SRP target structure and allocate an SRP information unit ring. + * @target: pointer to the SRP target structure to be initialized. + * @dev: device to be associated with the SRP target. + * @nr: number of elements the SRP receive ring will contain. + * @iu_size: size in bytes of a single information unit. + * + * Returns zero upon success and a negative error code upon failure. + */ int srp_target_alloc(struct srp_target *target, struct device *dev, size_t nr, size_t iu_size) { @@ -155,6 +193,7 @@ free_ring: } EXPORT_SYMBOL_GPL(srp_target_alloc); +/** Free the memory allocated by srp_target_alloc(). */ void srp_target_free(struct srp_target *target) { srp_ring_free(target->dev, target->rx_ring, target->rx_ring_size, @@ -163,6 +202,11 @@ void srp_target_free(struct srp_target *target) } EXPORT_SYMBOL_GPL(srp_target_free); +/** + * Get an information unit from the SRP target receive ring that is not in use. + * Initialize the ilist and flags members of the information unit before + * returning. + */ struct iu_entry *srp_iu_get(struct srp_target *target) { struct iu_entry *iue = NULL; @@ -177,12 +221,24 @@ struct iu_entry *srp_iu_get(struct srp_target *target) } EXPORT_SYMBOL_GPL(srp_iu_get); +/** Put an information unit back in the SRP target receive ring. */ void srp_iu_put(struct iu_entry *iue) { kfifo_put(iue->target->iu_queue.queue, (void *) &iue, sizeof(void *)); } EXPORT_SYMBOL_GPL(srp_iu_put); +/** + * Transfer the data referred to by an SRP direct data buffer descriptor + * via RDMA. + * @sc: SCSI command. + * @md: SRP direct data buffer descriptor. + * @dir: DMA data direction, the second last parameter passed to the function + * 'rdma_io'. + * @rdma_io: pointer to a callback function that performs the actual I/O. + * @dma_map: whether or not to map and unmap the scsi_sglist(sc). + * @ext_desc: ignored. + */ static int srp_direct_data(struct scsi_cmnd *sc, struct srp_direct_buf *md, enum dma_data_direction dir, srp_rdma_t rdma_io, int dma_map, int ext_desc) @@ -216,6 +272,17 @@ static int srp_direct_data(struct scsi_cmnd *sc, struct srp_direct_buf *md, return err; } +/** + * Transfer the data referred to by an SRP indirect data buffer descriptor via + * RDMA. + * @sc: SCSI command. + * @md: SRP indirect data buffer descriptor. + * @dir: DMA data direction, the second last parameter passed to the function + * 'rdma_io'. + * @rdma_io: pointer to a callback function that performs the actual I/O. + * @dma_map: whether or not to map and unmap the scsi_sglist(sc). + * @ext_desc: whether or not this command uses an external indirect buffer. + */ static int srp_indirect_data(struct scsi_cmnd *sc, struct srp_cmd *cmd, struct srp_indirect_buf *id, enum dma_data_direction dir, srp_rdma_t rdma_io, @@ -292,6 +359,10 @@ free_mem: return err; } +/** + * Compute the number of bytes occupied by the DATA-OUT descriptor in an + * SRP_CMD request. + */ static int data_out_desc_size(struct srp_cmd *cmd) { int size = 0; @@ -314,7 +385,16 @@ static int data_out_desc_size(struct srp_cmd *cmd) return size; } -/* +/** + * Transfer the data associated with an SRP_CMD request. + * @sc: SCSI command. + * @cmd: SRP_CMD request. + * @rdma_io: callback function for performing RDMA I/O. + * @dma_map: second-last parameter passed to rdma_io. + * @ext_desc: whether this command uses an external indirect buffer. + * + * Note: does not support bidirectional commands. + * * TODO: this can be called multiple times for a single command if it * has very long data. */ @@ -327,10 +407,23 @@ int srp_transfer_data(struct scsi_cmnd *sc, struct srp_cmd *cmd, int offset, err = 0; u8 format; + /* + * 'offset' is the offset in bytes of the data buffer descriptor in + * an SRP_CMD request. For an SRP request that transfers data from + * initiator to target, 'offset' is the offset of the data-out buffer + * descriptor. For an SRP request that transfers data from target to + * initiator, 'offset' is the offset of the data-in buffer descriptor. + * In an SRP_CMD request the following descriptors are present starting + * from cmd->add_data: additional CDB, data-out buffer descriptor and + * data-in buffer descriptor. + */ + + /* Skip over 'additional CDB' to start of data-out descriptor. */ offset = cmd->add_cdb_len * 4; dir = srp_cmd_direction(cmd); if (dir == DMA_FROM_DEVICE) + /* Skip over data-out descriptor to start of data-in. */ offset += data_out_desc_size(cmd); if (dir == DMA_TO_DEVICE) @@ -361,6 +454,13 @@ int srp_transfer_data(struct scsi_cmnd *sc, struct srp_cmd *cmd, } EXPORT_SYMBOL_GPL(srp_transfer_data); +/** + * Compute the size in bytes of one of the two data descriptors at the end of + * an SRP_CMD request. + * @cmd: SRP_CMD request. + * @dir: DMA_TO_DEVICE for the size of the data-out buffer descriptor; + * DMA_FROM_DEVICE for the size of the data-in buffer descriptor. + */ static int vscsis_data_length(struct srp_cmd *cmd, enum dma_data_direction dir) { struct srp_direct_buf *md; @@ -393,6 +493,10 @@ static int vscsis_data_length(struct srp_cmd *cmd, enum dma_data_direction dir) return len; } +/** + * Queue an SRP_CMD request for processing by appropriate target software, + * e.g. the user space process tgtd. + */ int srp_cmd_queue(struct Scsi_Host *shost, struct srp_cmd *cmd, void *info, u64 itn_id, u64 addr) { diff --git a/include/scsi/libsrp.h b/include/scsi/libsrp.h index ba615e4..e783830 100644 --- a/include/scsi/libsrp.h +++ b/include/scsi/libsrp.h @@ -1,11 +1,17 @@ #ifndef __LIBSRP_H__ #define __LIBSRP_H__ +/* + * Structures and constants exported by libsrp, a library for implementing + * SRP initiators and targets. + */ + #include #include #include #include +/* Names assigned to the bits of iu_entry::flags by the ibmvstgt driver. */ enum iue_flags { V_DIOVER, V_WRITE, @@ -13,43 +19,73 @@ enum iue_flags { V_FLYING, }; +/* SRP data buffer as managed by libsrp. */ struct srp_buf { dma_addr_t dma; void *buf; }; +/* Pool of SRP information units. */ struct srp_queue { + /* kfifo storage; an array of n struct iu_entry* items. */ void *pool; + /* information unit storage; an array of n struct iu_entry items. */ void *items; + /* kfifo containing pointers to iu_entry items currently not in use. */ struct kfifo *queue; + /* spinlock associated with the above kfifo. */ spinlock_t lock; }; +/* SRP target. */ struct srp_target { + /* Pointer to the SCSI host associated with the SRP target. */ struct Scsi_Host *shost; + /* Pointer to the device node associated with the SRP target. */ struct device *dev; + /* Initialized but not used otherwise inside libsrp. */ spinlock_t lock; + /* Initialized but not used otherwise inside libsrp. */ struct list_head cmd_queue; + /* Size in bytes of a single information unit. */ size_t srp_iu_size; + /* Information unit receive ring. */ struct srp_queue iu_queue; + /* Number of elements in the information unit receive ring. */ size_t rx_ring_size; + /* Pointer to an array of SRP buffers associated with the rx ring. */ struct srp_buf **rx_ring; + /* Pointer to target-private data. */ void *ldata; }; +/* Information unit as processed by an SRP target. */ struct iu_entry { + /* Backpointer to the SRP target processing this information unit. */ struct srp_target *target; + /* Used by ibmvscsi for insertion in the srp_target::cmd_queue list. */ struct list_head ilist; + /* Used by the ibmvscsi driver but not by libsrp. */ dma_addr_t remote_token; + /* Initialized by libsrp but not used otherwise by libsrp. */ unsigned long flags; + /* SRP buffer associated with this information unit. */ struct srp_buf *sbuf; }; +/* + * Pointer to a callback function that performs RDMA I/O. + * + * Arguments (in order): SCSI command pointer, scatterlist pointer, + * number of entries in the scatterlist, pointer to an array of SRP + * memory descriptor pointers, number of elements in this array, DMA + * data direction, maximum number of bytes to transfer. + */ typedef int (srp_rdma_t)(struct scsi_cmnd *, struct scatterlist *, int, struct srp_direct_buf *, int, enum dma_data_direction, unsigned int); @@ -69,6 +105,16 @@ static inline struct srp_target *host_to_srp_target(struct Scsi_Host *host) return (struct srp_target *) host->hostdata; } +/* + * Find out whether an SRP_CMD request is transferring data from initiator to + * target or from target to initiator. + * + * Returns DMA_TO_DEVICE when transferring data from initiator to target and + * DMA_FROM_DEVICE when transferring data from target to initiator. This + * reflects the point of view of an SRP initiator implementation. + * + * Note: do not use this function for bidirectional commands. + */ static inline int srp_cmd_direction(struct srp_cmd *cmd) { return (cmd->buf_fmt >> 4) ? DMA_TO_DEVICE : DMA_FROM_DEVICE; diff --git a/include/scsi/srp.h b/include/scsi/srp.h index ad178fa..ebb6096 100644 --- a/include/scsi/srp.h +++ b/include/scsi/srp.h @@ -38,11 +38,13 @@ /* * Structures and constants for the SCSI RDMA Protocol (SRP) as * defined by the INCITS T10 committee. This file was written using - * draft Revision 16a of the SRP standard. + * draft Revision 16a of the SRP standard. See also + * http://www.t10.org/drafts.htm#SCSI3_SRP. */ #include +/* SRP information unit types. */ enum { SRP_LOGIN_REQ = 0x00, SRP_TSK_MGMT = 0x01, @@ -58,17 +60,31 @@ enum { SRP_AER_RSP = 0x42 }; +/* + * Flags for the 'REQUIRED BUFFER FORMATS' field of the SRP_LOGIN_REQ request + * (srp_login_req::req_buf_fmt) or the 'SUPPORTED BUFFER FORMATS' field of the + * SRP_LOGIN_RSP response (srp_login_rsp::buf_fmt). See also section 5.6.2.2 + * in the T10 SRP r16a document. + */ enum { SRP_BUF_FORMAT_DIRECT = 1 << 1, SRP_BUF_FORMAT_INDIRECT = 1 << 2 }; +/* + * Format of data-in and data-out buffer descriptors in an SRP_CMD + * request. See also section 5.6.2.1 in the T10 SRP r16a document. + */ enum { SRP_NO_DATA_DESC = 0, SRP_DATA_DESC_DIRECT = 1, SRP_DATA_DESC_INDIRECT = 2 }; +/* + * Allowed values for the 'TASK MANAGEMENT FUNCTION' field of the SRP_TSK_MGMT + * request. See also section 6.7 in the T10 SRP r16a document. + */ enum { SRP_TSK_ABORT_TASK = 0x01, SRP_TSK_ABORT_TASK_SET = 0x02, @@ -77,6 +93,10 @@ enum { SRP_TSK_CLEAR_ACA = 0x40 }; +/* + * Allowed values for the 'REASON' field of the SRP_LOGIN_REJ response. See + * also section 6.4 in the T10 SRP r16a document. + */ enum srp_login_rej_reason { SRP_LOGIN_REJ_UNABLE_ESTABLISH_CHANNEL = 0x00010000, SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES = 0x00010001, @@ -87,11 +107,20 @@ enum srp_login_rej_reason { SRP_LOGIN_REJ_CHANNEL_LIMIT_REACHED = 0x00010006 }; +/* + * IB I/O class assigned to revisions 10 and r16a of the SRP protocol. + * See also section B.7 in the T10 SRP r16a document. + */ enum { SRP_REV10_IB_IO_CLASS = 0xff00, SRP_REV16A_IB_IO_CLASS = 0x0100 }; +/* + * Direct data buffer descriptor as defined in section 5.6.2.4 of the T10 SRP + * r16a document. Each direct data buffer descriptor consists of a virtual + * address, a memory handle and a data length. + */ struct srp_direct_buf { __be64 va; __be32 key; @@ -99,6 +128,9 @@ struct srp_direct_buf { }; /* + * Indirect data buffer descriptor as defined in section 5.6.2.5 of the T10 + * SRP r16a document. + * * We need the packed attribute because the SRP spec puts the list of * descriptors at an offset of 20, which is not aligned to the size of * struct srp_direct_buf. The whole structure must be packed to avoid @@ -110,11 +142,20 @@ struct srp_indirect_buf { struct srp_direct_buf desc_list[0]; } __attribute__((packed)); +/* + * Allowed values for the 'MULTI-CHANNEL ACTION CODE' field of the + * SRP_LOGIN_REQ request, as defined in section 6.2 of the T10 SRP r16a + * document. + */ enum { SRP_MULTICHAN_SINGLE = 0, SRP_MULTICHAN_MULTI = 1 }; +/* + * SRP_LOGIN_REQ request, also defined in section 6.2 of the T10 SRP r16a + * document. + */ struct srp_login_req { u8 opcode; u8 reserved1[7]; @@ -129,6 +170,9 @@ struct srp_login_req { }; /* + * SRP_LOGIN_RSP response, as defined in section 6.3 of the T10 SRP r16a + * document. + * * The SRP spec defines the size of the LOGIN_RSP structure to be 52 * bytes, so it needs to be packed to avoid having it padded to 56 * bytes on 64-bit architectures. @@ -145,6 +189,10 @@ struct srp_login_rsp { u8 reserved2[25]; } __attribute__((packed)); +/* + * SRP_LOGIN_REJ response, as defined in section 6.4 of the T10 SRP r16a + * document. + */ struct srp_login_rej { u8 opcode; u8 reserved1[3]; @@ -155,12 +203,19 @@ struct srp_login_rej { u8 reserved3[6]; }; +/* + * SRP_I_LOGOUT request, as defined in section 6.5 of the T10 SRP r16a + * document. + */ struct srp_i_logout { u8 opcode; u8 reserved[7]; u64 tag; }; +/* + * SRP_T_LOGOUT request, as defined in section 6.6 of the T10 SRP r16a document. + */ struct srp_t_logout { u8 opcode; u8 sol_not; @@ -170,6 +225,8 @@ struct srp_t_logout { }; /* + * SRP_TSK_MGMT request, as defined in section 6.7 of the T10 SRP r16a document. + * * We need the packed attribute because the SRP spec only aligns the * 8-byte LUN field to 4 bytes. */ @@ -188,6 +245,9 @@ struct srp_tsk_mgmt { }; /* + * SRP_CMD request with a single CDB as defined in section 6.8 of the T10 SRP + * r16a document. + * * We need the packed attribute because the SRP spec only aligns the * 8-byte LUN field to 4 bytes. */ @@ -209,6 +269,10 @@ struct srp_cmd { u8 add_data[0]; }; +/* + * Allowed flags for the flags field of the SRP_RSP response. See also + * section 6.9 of the T10 SRP r16a document. + */ enum { SRP_RSP_FLAG_RSPVALID = 1 << 0, SRP_RSP_FLAG_SNSVALID = 1 << 1, @@ -219,6 +283,8 @@ enum { }; /* + * SRP_RSP response, as defined in section 6.9 of the T10 SRP r16a document. + * * The SRP spec defines the size of the RSP structure to be 36 bytes, * so it needs to be packed to avoid having it padded to 40 bytes on * 64-bit architectures.