fcp.c

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/*
 * Copyright (C) 2010 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <assert.h>
#include <byteswap.h>
#include <ipxe/refcnt.h>
#include <ipxe/list.h>
#include <ipxe/interface.h>
#include <ipxe/xfer.h>
#include <ipxe/iobuf.h>
#include <ipxe/open.h>
#include <ipxe/process.h>
#include <ipxe/uri.h>
#include <ipxe/acpi.h>
#include <ipxe/scsi.h>
#include <ipxe/device.h>
#include <ipxe/edd.h>
#include <ipxe/efi/efi_path.h>
#include <ipxe/fc.h>
#include <ipxe/fcels.h>
#include <ipxe/fcp.h>

/** @file
 *
 * Fibre Channel Protocol
 *
 */

/* Disambiguate the various error causes */
#define ERANGE_READ_DATA_ORDERING \
        __einfo_error ( EINFO_ERANGE_READ_DATA_ORDERING )
#define EINFO_ERANGE_READ_DATA_ORDERING \
        __einfo_uniqify ( EINFO_ERANGE, 0x01, "Read data out of order" )
#define ERANGE_READ_DATA_OVERRUN \
        __einfo_error ( EINFO_ERANGE_READ_DATA_OVERRUN )
#define EINFO_ERANGE_READ_DATA_OVERRUN \
        __einfo_uniqify ( EINFO_ERANGE, 0x02, "Read data overrun" )
#define ERANGE_WRITE_DATA_STUCK \
        __einfo_error ( EINFO_ERANGE_WRITE_DATA_STUCK )
#define EINFO_ERANGE_WRITE_DATA_STUCK \
        __einfo_uniqify ( EINFO_ERANGE, 0x03, "Write data stuck" )
#define ERANGE_WRITE_DATA_OVERRUN \
        __einfo_error ( EINFO_ERANGE_WRITE_DATA_OVERRUN )
#define EINFO_ERANGE_WRITE_DATA_OVERRUN \
        __einfo_uniqify ( EINFO_ERANGE, 0x04, "Write data overrun" )
#define ERANGE_DATA_UNDERRUN \
        __einfo_error ( EINFO_ERANGE_DATA_UNDERRUN )
#define EINFO_ERANGE_DATA_UNDERRUN \
        __einfo_uniqify ( EINFO_ERANGE, 0x05, "Data underrun" )

/******************************************************************************
 *
 * PRLI
 *
 ******************************************************************************
 */

struct fc_els_prli_descriptor fcp_prli_descriptor __fc_els_prli_descriptor;

/**
 * Transmit FCP PRLI
 *
 * @v els               Fibre Channel ELS transaction
 * @ret rc              Return status code
 */
static int fcp_prli_tx ( struct fc_els *els ) {
        struct fcp_prli_service_parameters param;

        /* Build service parameter page */
        memset ( &param, 0, sizeof ( param ) );
        param.flags = htonl ( FCP_PRLI_NO_READ_RDY | FCP_PRLI_INITIATOR );

        return fc_els_prli_tx ( els, &fcp_prli_descriptor, &param );
}

/**
 * Receive FCP PRLI
 *
 * @v els               Fibre Channel ELS transaction
 * @v frame             ELS frame
 * @v len               Length of ELS frame
 * @ret rc              Return status code
 */
static int fcp_prli_rx ( struct fc_els *els, void *data, size_t len ) {
        return fc_els_prli_rx ( els, &fcp_prli_descriptor, data, len );
}

/**
 * Detect FCP PRLI
 *
 * @v els               Fibre Channel ELS transaction
 * @v data              ELS frame
 * @v len               Length of ELS frame
 * @ret rc              Return status code
 */
static int fcp_prli_detect ( struct fc_els *els, const void *data,
                             size_t len ) {
        return fc_els_prli_detect ( els, &fcp_prli_descriptor, data, len );
}

/** FCP PRLI ELS handler */
struct fc_els_handler fcp_prli_handler __fc_els_handler = {
        .name           = "PRLI-FCP",
        .tx             = fcp_prli_tx,
        .rx             = fcp_prli_rx,
        .detect         = fcp_prli_detect,
};

/** FCP PRLI descriptor */
struct fc_els_prli_descriptor fcp_prli_descriptor __fc_els_prli_descriptor = {
        .type           = FC_TYPE_FCP,
        .param_len      = sizeof ( struct fcp_prli_service_parameters ),
        .handler        = &fcp_prli_handler,
};

/******************************************************************************
 *
 * FCP devices and commands
 *
 ******************************************************************************
 */

/** An FCP device */
struct fcp_device {
        /** Reference count */
        struct refcnt refcnt;
        /** Fibre Channel upper-layer protocol user */
        struct fc_ulp_user user;
        /** SCSI command issuing interface */
        struct interface scsi;
        /** List of active commands */
        struct list_head fcpcmds;

        /** Device description (for boot firmware table) */
        struct fcp_description desc;
};

/** An FCP command */
struct fcp_command {
        /** Reference count */
        struct refcnt refcnt;
        /** FCP SCSI device */
        struct fcp_device *fcpdev;
        /** List of active commands */
        struct list_head list;
        /** SCSI command interface */
        struct interface scsi;
        /** Fibre Channel exchange interface */
        struct interface xchg;
        /** Send process */
        struct process process;
        /** Send current IU
         *
         * @v fcpcmd    FCP command
         * @ret rc      Return status code
         */
        int ( * send ) ( struct fcp_command *fcpcmd );
        /** SCSI command */
        struct scsi_cmd command;
        /** Data offset within command */
        size_t offset;
        /** Length of data remaining to be sent within this IU */
        size_t remaining;
        /** Exchange ID */
        uint16_t xchg_id;
};

/**
 * Get reference to FCP device
 *
 * @v fcpdev            FCP device
 * @ret fcpdev          FCP device
 */
static inline __attribute__ (( always_inline )) struct fcp_device *
fcpdev_get ( struct fcp_device *fcpdev ) {
        ref_get ( &fcpdev->refcnt );
        return fcpdev;
}

/**
 * Drop reference to FCP device
 *
 * @v fcpdev            FCP device
 */
static inline __attribute__ (( always_inline )) void
fcpdev_put ( struct fcp_device *fcpdev ) {
        ref_put ( &fcpdev->refcnt );
}

/**
 * Get reference to FCP command
 *
 * @v fcpcmd            FCP command
 * @ret fcpcmd          FCP command
 */
static inline __attribute__ (( always_inline )) struct fcp_command *
fcpcmd_get ( struct fcp_command *fcpcmd ) {
        ref_get ( &fcpcmd->refcnt );
        return fcpcmd;
}

/**
 * Drop reference to FCP command
 *
 * @v fcpcmd            FCP command
 */
static inline __attribute__ (( always_inline )) void
fcpcmd_put ( struct fcp_command *fcpcmd ) {
        ref_put ( &fcpcmd->refcnt );
}

/**
 * Start FCP command sending
 *
 * @v fcpcmd            FCP command
 * @v send              Send method
 */
static inline __attribute__ (( always_inline )) void
fcpcmd_start_send ( struct fcp_command *fcpcmd,
                    int ( * send ) ( struct fcp_command *fcpcmd ) ) {
        fcpcmd->send = send;
        process_add ( &fcpcmd->process );
}

/**
 * Stop FCP command sending
 *
 * @v fcpcmd            FCP command
 */
static inline __attribute__ (( always_inline )) void
fcpcmd_stop_send ( struct fcp_command *fcpcmd ) {
        process_del ( &fcpcmd->process );
}

/**
 * Free FCP command
 *
 * @v refcnt            Reference count
 */
static void fcpcmd_free ( struct refcnt *refcnt ) {
        struct fcp_command *fcpcmd =
                container_of ( refcnt, struct fcp_command, refcnt );

        /* Remove from list of commands */
        list_del ( &fcpcmd->list );
        fcpdev_put ( fcpcmd->fcpdev );

        /* Free command */
        free ( fcpcmd );
}

/**
 * Close FCP command
 *
 * @v fcpcmd            FCP command
 * @v rc                Reason for close
 */
static void fcpcmd_close ( struct fcp_command *fcpcmd, int rc ) {
        struct fcp_device *fcpdev = fcpcmd->fcpdev;

        if ( rc != 0 ) {
                DBGC ( fcpdev, "FCP %p xchg %04x closed: %s\n",
                       fcpdev, fcpcmd->xchg_id, strerror ( rc ) );
        }

        /* Stop sending */
        fcpcmd_stop_send ( fcpcmd );

        /* Shut down interfaces */
        intf_shutdown ( &fcpcmd->scsi, rc );
        intf_shutdown ( &fcpcmd->xchg, rc );
}

/**
 * Close FCP command in error
 *
 * @v fcpcmd            FCP command
 * @v rc                Reason for close
 */
static void fcpcmd_close_err ( struct fcp_command *fcpcmd, int rc ) {
        if ( rc == 0 )
                rc = -EPIPE;
        fcpcmd_close ( fcpcmd, rc );
}

/**
 * Send FCP command IU
 *
 * @v fcpcmd            FCP command
 * @ret rc              Return status code
 */
static int fcpcmd_send_cmnd ( struct fcp_command *fcpcmd ) {
        struct fcp_device *fcpdev = fcpcmd->fcpdev;
        struct scsi_cmd *command = &fcpcmd->command;
        struct io_buffer *iobuf;
        struct fcp_cmnd *cmnd;
        struct xfer_metadata meta;
        int rc;

        /* Sanity check */
        if ( command->data_in_len && command->data_out_len ) {
                DBGC ( fcpdev, "FCP %p xchg %04x cannot handle bidirectional "
                       "command\n", fcpdev, fcpcmd->xchg_id );
                return -ENOTSUP;
        }

        /* Allocate I/O buffer */
        iobuf = xfer_alloc_iob ( &fcpcmd->xchg, sizeof ( *cmnd ) );
        if ( ! iobuf ) {
                DBGC ( fcpdev, "FCP %p xchg %04x cannot allocate command IU\n",
                       fcpdev, fcpcmd->xchg_id );
                return -ENOMEM;
        }

        /* Construct command IU frame */
        cmnd = iob_put ( iobuf, sizeof ( *cmnd ) );
        memset ( cmnd, 0, sizeof ( *cmnd ) );
        memcpy ( &cmnd->lun, &command->lun, sizeof ( cmnd->lun ) );
        assert ( ! ( command->data_in_len && command->data_out_len ) );
        if ( command->data_in_len )
                cmnd->dirn |= FCP_CMND_RDDATA;
        if ( command->data_out_len )
                cmnd->dirn |= FCP_CMND_WRDATA;
        memcpy ( &cmnd->cdb, &fcpcmd->command.cdb, sizeof ( cmnd->cdb ) );
        cmnd->len = htonl ( command->data_in_len + command->data_out_len );
        memset ( &meta, 0, sizeof ( meta ) );
        meta.flags = ( XFER_FL_CMD_STAT | XFER_FL_OVER );
        DBGC2 ( fcpdev, "FCP %p xchg %04x CMND " SCSI_CDB_FORMAT " %04x\n",
                fcpdev, fcpcmd->xchg_id, SCSI_CDB_DATA ( cmnd->cdb ),
                ntohl ( cmnd->len ) );

        /* No further data to send within this IU */
        fcpcmd_stop_send ( fcpcmd );

        /* Send command IU frame */
        if ( ( rc = xfer_deliver ( &fcpcmd->xchg, iob_disown ( iobuf ),
                                   &meta ) ) != 0 ) {
                DBGC ( fcpdev, "FCP %p xchg %04x cannot deliver command IU: "
                       "%s\n", fcpdev, fcpcmd->xchg_id, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Handle FCP read data IU
 *
 * @v fcpcmd            FCP command
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int fcpcmd_recv_rddata ( struct fcp_command *fcpcmd,
                                struct io_buffer *iobuf,
                                struct xfer_metadata *meta ) {
        struct fcp_device *fcpdev = fcpcmd->fcpdev;
        struct scsi_cmd *command = &fcpcmd->command;
        size_t offset = meta->offset;
        size_t len = iob_len ( iobuf );
        int rc;

        /* Sanity checks */
        if ( ! ( meta->flags & XFER_FL_ABS_OFFSET ) ) {
                DBGC ( fcpdev, "FCP %p xchg %04x read data missing offset\n",
                       fcpdev, fcpcmd->xchg_id );
                rc = -ERANGE_READ_DATA_ORDERING;
                goto done;
        }
        if ( offset != fcpcmd->offset ) {
                DBGC ( fcpdev, "FCP %p xchg %04x read data out of order "
                       "(expected %zd, received %zd)\n",
                       fcpdev, fcpcmd->xchg_id, fcpcmd->offset, offset );
                rc = -ERANGE_READ_DATA_ORDERING;
                goto done;
        }
        if ( ( offset + len ) > command->data_in_len ) {
                DBGC ( fcpdev, "FCP %p xchg %04x read data overrun (max %zd, "
                       "received %zd)\n", fcpdev, fcpcmd->xchg_id,
                       command->data_in_len, ( offset + len ) );
                rc = -ERANGE_READ_DATA_OVERRUN;
                goto done;
        }
        DBGC2 ( fcpdev, "FCP %p xchg %04x RDDATA [%08zx,%08zx)\n",
                fcpdev, fcpcmd->xchg_id, offset, ( offset + len ) );

        /* Copy to user buffer */
        copy_to_user ( command->data_in, offset, iobuf->data, len );
        fcpcmd->offset += len;
        assert ( fcpcmd->offset <= command->data_in_len );

        rc = 0;
 done:
        free_iob ( iobuf );
        return rc;
}

/**
 * Send FCP write data IU
 *
 * @v fcpcmd            FCP command
 * @ret rc              Return status code
 */
static int fcpcmd_send_wrdata ( struct fcp_command *fcpcmd ) {
        struct fcp_device *fcpdev = fcpcmd->fcpdev;
        struct scsi_cmd *command = &fcpcmd->command;
        struct io_buffer *iobuf;
        struct xfer_metadata meta;
        size_t len;
        int rc;

        /* Calculate length to be sent */
        len = xfer_window ( &fcpcmd->xchg );
        if ( len > fcpcmd->remaining )
                len = fcpcmd->remaining;

        /* Sanity checks */
        if ( len == 0 ) {
                DBGC ( fcpdev, "FCP %p xchg %04x write data stuck\n",
                       fcpdev, fcpcmd->xchg_id );
                return -ERANGE_WRITE_DATA_STUCK;
        }
        if ( ( fcpcmd->offset + len ) > command->data_out_len ) {
                DBGC ( fcpdev, "FCP %p xchg %04x write data overrun (max %zd, "
                       "requested %zd)\n", fcpdev, fcpcmd->xchg_id,
                       command->data_out_len, ( fcpcmd->offset + len ) );
                return -ERANGE_WRITE_DATA_OVERRUN;
        }

        /* Allocate I/O buffer */
        iobuf = xfer_alloc_iob ( &fcpcmd->xchg, len );
        if ( ! iobuf ) {
                DBGC ( fcpdev, "FCP %p xchg %04x cannot allocate write data "
                       "IU for %zd bytes\n", fcpdev, fcpcmd->xchg_id, len );
                return -ENOMEM;
        }

        /* Construct data IU frame */
        copy_from_user ( iob_put ( iobuf, len ), command->data_out,
                         fcpcmd->offset, len );
        memset ( &meta, 0, sizeof ( meta ) );
        meta.flags = ( XFER_FL_RESPONSE | XFER_FL_ABS_OFFSET );
        meta.offset = fcpcmd->offset;
        DBGC2 ( fcpdev, "FCP %p xchg %04x WRDATA [%08zx,%04zx)\n",
                fcpdev, fcpcmd->xchg_id, fcpcmd->offset,
                ( fcpcmd->offset + iob_len ( iobuf ) ) );

        /* Calculate amount of data remaining to be sent within this IU */
        assert ( len <= fcpcmd->remaining );
        fcpcmd->offset += len;
        fcpcmd->remaining -= len;
        assert ( fcpcmd->offset <= command->data_out_len );
        if ( fcpcmd->remaining == 0 ) {
                fcpcmd_stop_send ( fcpcmd );
                meta.flags |= XFER_FL_OVER;
        }

        /* Send data IU frame */
        if ( ( rc = xfer_deliver ( &fcpcmd->xchg, iob_disown ( iobuf ),
                                   &meta ) ) != 0 ) {
                DBGC ( fcpdev, "FCP %p xchg %04x cannot deliver write data "
                       "IU: %s\n", fcpdev, fcpcmd->xchg_id, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Handle FCP transfer ready IU
 *
 * @v fcpcmd            FCP command
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int fcpcmd_recv_xfer_rdy ( struct fcp_command *fcpcmd,
                                  struct io_buffer *iobuf,
                                  struct xfer_metadata *meta __unused ) {
        struct fcp_device *fcpdev = fcpcmd->fcpdev;
        struct fcp_xfer_rdy *xfer_rdy = iobuf->data;
        int rc;

        /* Sanity checks */
        if ( iob_len ( iobuf ) != sizeof ( *xfer_rdy ) ) {
                DBGC ( fcpdev, "FCP %p xchg %04x received invalid transfer "
                       "ready IU:\n", fcpdev, fcpcmd->xchg_id );
                DBGC_HDA ( fcpdev, 0, iobuf->data, iob_len ( iobuf ) );
                rc = -EPROTO;
                goto done;
        }
        if ( ntohl ( xfer_rdy->offset ) != fcpcmd->offset ) {
                /* We do not advertise out-of-order delivery */
                DBGC ( fcpdev, "FCP %p xchg %04x cannot support out-of-order "
                       "delivery (expected %zd, requested %d)\n",
                       fcpdev, fcpcmd->xchg_id, fcpcmd->offset,
                       ntohl ( xfer_rdy->offset ) );
                rc = -EPROTO;
                goto done;
        }
        DBGC2 ( fcpdev, "FCP %p xchg %04x XFER_RDY [%08x,%08x)\n",
                fcpdev, fcpcmd->xchg_id, ntohl ( xfer_rdy->offset ),
                ( ntohl ( xfer_rdy->offset ) + ntohl ( xfer_rdy->len ) ) );

        /* Start sending requested data */
        fcpcmd->remaining = ntohl ( xfer_rdy->len );
        fcpcmd_start_send ( fcpcmd, fcpcmd_send_wrdata );

        rc = 0;
 done:
        free_iob ( iobuf );
        return rc;
}

/**
 * Handle FCP response IU
 *
 * @v fcpcmd            FCP command
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int fcpcmd_recv_rsp ( struct fcp_command *fcpcmd,
                             struct io_buffer *iobuf,
                             struct xfer_metadata *meta __unused ) {
        struct fcp_device *fcpdev = fcpcmd->fcpdev;
        struct scsi_cmd *command = &fcpcmd->command;
        struct fcp_rsp *rsp = iobuf->data;
        struct scsi_rsp response;
        int rc;

        /* Sanity check */
        if ( ( iob_len ( iobuf ) < sizeof ( *rsp ) ) ||
             ( iob_len ( iobuf ) < ( sizeof ( *rsp ) +
                                     fcp_rsp_response_data_len ( rsp ) +
                                     fcp_rsp_sense_data_len ( rsp ) ) ) ) {
                DBGC ( fcpdev, "FCP %p xchg %04x received invalid response "
                       "IU:\n", fcpdev, fcpcmd->xchg_id );
                DBGC_HDA ( fcpdev, 0, iobuf->data, iob_len ( iobuf ) );
                rc = -EPROTO;
                goto done;
        }
        DBGC2 ( fcpdev, "FCP %p xchg %04x RSP stat %02x resid %08x flags %02x"
                "%s%s%s%s\n", fcpdev, fcpcmd->xchg_id, rsp->status,
                ntohl ( rsp->residual ), rsp->flags,
                ( ( rsp->flags & FCP_RSP_RESPONSE_LEN_VALID ) ? " resp" : "" ),
                ( ( rsp->flags & FCP_RSP_SENSE_LEN_VALID ) ? " sense" : "" ),
                ( ( rsp->flags & FCP_RSP_RESIDUAL_OVERRUN ) ? " over" : "" ),
                ( ( rsp->flags & FCP_RSP_RESIDUAL_UNDERRUN ) ? " under" : "" ));
        if ( fcp_rsp_response_data ( rsp ) ) {
                DBGC2 ( fcpdev, "FCP %p xchg %04x response data:\n",
                        fcpdev, fcpcmd->xchg_id );
                DBGC2_HDA ( fcpdev, 0, fcp_rsp_response_data ( rsp ),
                            fcp_rsp_response_data_len ( rsp ) );
        }
        if ( fcp_rsp_sense_data ( rsp ) ) {
                DBGC2 ( fcpdev, "FCP %p xchg %04x sense data:\n",
                        fcpdev, fcpcmd->xchg_id );
                DBGC2_HDA ( fcpdev, 0, fcp_rsp_sense_data ( rsp ),
                            fcp_rsp_sense_data_len ( rsp ) );
        }

        /* Check for locally-detected command underrun */
        if ( ( rsp->status == 0 ) &&
             ( fcpcmd->offset != ( command->data_in_len +
                                   command->data_out_len ) ) ) {
                DBGC ( fcpdev, "FCP %p xchg %04x data underrun (expected %zd, "
                       "got %zd)\n", fcpdev, fcpcmd->xchg_id,
                       ( command->data_in_len + command->data_out_len ),
                       fcpcmd->offset );
                rc = -ERANGE_DATA_UNDERRUN;
                goto done;
        }

        /* Build SCSI response */
        memset ( &response, 0, sizeof ( response ) );
        response.status = rsp->status;
        if ( rsp->flags & ( FCP_RSP_RESIDUAL_OVERRUN |
                            FCP_RSP_RESIDUAL_UNDERRUN ) ) {
                response.overrun = ntohl ( rsp->residual );
                if ( rsp->flags & FCP_RSP_RESIDUAL_UNDERRUN )
                        response.overrun = -response.overrun;
        }
        scsi_parse_sense ( fcp_rsp_sense_data ( rsp ),
                           fcp_rsp_sense_data_len ( rsp ), &response.sense );

        /* Free buffer before sending response, to minimise
         * out-of-memory errors.
         */
        free_iob ( iob_disown ( iobuf ) );

        /* Send SCSI response */
        scsi_response ( &fcpcmd->scsi, &response );

        /* Terminate command */
        fcpcmd_close ( fcpcmd, 0 );

        rc = 0;
 done:
        free_iob ( iobuf );
        return rc;
}

/**
 * Handle unknown FCP IU
 *
 * @v fcpcmd            FCP command
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int fcpcmd_recv_unknown ( struct fcp_command *fcpcmd,
                                 struct io_buffer *iobuf,
                                 struct xfer_metadata *meta __unused ) {
        struct fcp_device *fcpdev = fcpcmd->fcpdev;

        DBGC ( fcpdev, "FCP %p xchg %04x received unknown IU:\n",
               fcpdev, fcpcmd->xchg_id );
        DBGC_HDA ( fcpdev, 0, iobuf->data, iob_len ( iobuf ) );
        free_iob ( iobuf );
        return -EPROTO;
}

/**
 * Transmit FCP frame
 *
 * @v fcpcmd            FCP command
 */
static void fcpcmd_step ( struct fcp_command *fcpcmd ) {
        int rc;

        /* Send the current IU */
        if ( ( rc = fcpcmd->send ( fcpcmd ) ) != 0 ) {
                /* Treat failure as a fatal error */
                fcpcmd_close ( fcpcmd, rc );
        }
}

/**
 * Receive FCP frame
 *
 * @v fcpcmd            FCP command
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int fcpcmd_deliver ( struct fcp_command *fcpcmd,
                            struct io_buffer *iobuf,
                            struct xfer_metadata *meta ) {
        int ( * fcpcmd_recv ) ( struct fcp_command *fcpcmd,
                                struct io_buffer *iobuf,
                                struct xfer_metadata *meta );
        int rc;

        /* Determine handler */
        switch ( meta->flags & ( XFER_FL_CMD_STAT | XFER_FL_RESPONSE ) ) {
        case ( XFER_FL_RESPONSE ) :
                fcpcmd_recv = fcpcmd_recv_rddata;
                break;
        case ( XFER_FL_CMD_STAT ) :
                fcpcmd_recv = fcpcmd_recv_xfer_rdy;
                break;
        case ( XFER_FL_CMD_STAT | XFER_FL_RESPONSE ) :
                fcpcmd_recv = fcpcmd_recv_rsp;
                break;
        default:
                fcpcmd_recv = fcpcmd_recv_unknown;
                break;
        }

        /* Handle IU */
        if ( ( rc = fcpcmd_recv ( fcpcmd, iob_disown ( iobuf ), meta ) ) != 0 ){
                /* Treat any error as fatal to the command */
                fcpcmd_close ( fcpcmd, rc );
        }

        return rc;
}

/** FCP command SCSI interface operations */
static struct interface_operation fcpcmd_scsi_op[] = {
        INTF_OP ( intf_close, struct fcp_command *, fcpcmd_close ),
};

/** FCP command SCSI interface descriptor */
static struct interface_descriptor fcpcmd_scsi_desc =
        INTF_DESC_PASSTHRU ( struct fcp_command, scsi, fcpcmd_scsi_op, xchg );

/** FCP command Fibre Channel exchange interface operations */
static struct interface_operation fcpcmd_xchg_op[] = {
        INTF_OP ( xfer_deliver, struct fcp_command *, fcpcmd_deliver ),
        INTF_OP ( intf_close, struct fcp_command *, fcpcmd_close_err ),
};

/** FCP command Fibre Channel exchange interface descriptor */
static struct interface_descriptor fcpcmd_xchg_desc =
        INTF_DESC_PASSTHRU ( struct fcp_command, xchg, fcpcmd_xchg_op, scsi );

/** FCP command process descriptor */
static struct process_descriptor fcpcmd_process_desc =
        PROC_DESC ( struct fcp_command, process, fcpcmd_step );

/**
 * Issue FCP SCSI command
 *
 * @v fcpdev            FCP device
 * @v parent            Parent interface
 * @v command           SCSI command
 * @ret tag             Command tag, or negative error
 */
static int fcpdev_scsi_command ( struct fcp_device *fcpdev,
                                 struct interface *parent,
                                 struct scsi_cmd *command ) {
        struct fcp_prli_service_parameters *param = fcpdev->user.ulp->param;
        struct fcp_command *fcpcmd;
        int xchg_id;
        int rc;

        /* Check link */
        if ( ( rc = fcpdev->user.ulp->link.rc ) != 0 ) {
                DBGC ( fcpdev, "FCP %p could not issue command while link is "
                       "down: %s\n", fcpdev, strerror ( rc ) );
                goto err_link;
        }

        /* Check target capability */
        assert ( param != NULL );
        assert ( fcpdev->user.ulp->param_len >= sizeof ( *param ) );
        if ( ! ( param->flags & htonl ( FCP_PRLI_TARGET ) ) ) {
                DBGC ( fcpdev, "FCP %p could not issue command: not a target\n",
                       fcpdev );
                rc = -ENOTTY;
                goto err_target;
        }

        /* Allocate and initialise structure */
        fcpcmd = zalloc ( sizeof ( *fcpcmd ) );
        if ( ! fcpcmd ) {
                rc = -ENOMEM;
                goto err_zalloc;
        }
        ref_init ( &fcpcmd->refcnt, fcpcmd_free );
        intf_init ( &fcpcmd->scsi, &fcpcmd_scsi_desc, &fcpcmd->refcnt );
        intf_init ( &fcpcmd->xchg, &fcpcmd_xchg_desc, &fcpcmd->refcnt );
        process_init_stopped ( &fcpcmd->process, &fcpcmd_process_desc,
                               &fcpcmd->refcnt );
        fcpcmd->fcpdev = fcpdev_get ( fcpdev );
        list_add ( &fcpcmd->list, &fcpdev->fcpcmds );
        memcpy ( &fcpcmd->command, command, sizeof ( fcpcmd->command ) );

        /* Create new exchange */
        if ( ( xchg_id = fc_xchg_originate ( &fcpcmd->xchg,
                                             fcpdev->user.ulp->peer->port,
                                             &fcpdev->user.ulp->peer->port_id,
                                             FC_TYPE_FCP ) ) < 0 ) {
                rc = xchg_id;
                DBGC ( fcpdev, "FCP %p could not create exchange: %s\n",
                       fcpdev, strerror ( rc ) );
                goto err_xchg_originate;
        }
        fcpcmd->xchg_id = xchg_id;

        /* Start sending command IU */
        fcpcmd_start_send ( fcpcmd, fcpcmd_send_cmnd );

        /* Attach to parent interface, mortalise self, and return */
        intf_plug_plug ( &fcpcmd->scsi, parent );
        ref_put ( &fcpcmd->refcnt );
        return ( FCP_TAG_MAGIC | fcpcmd->xchg_id );

 err_xchg_originate:
        fcpcmd_close ( fcpcmd, rc );
        ref_put ( &fcpcmd->refcnt );
 err_zalloc:
 err_target:
 err_link:
        return rc;
}

/**
 * Close FCP device
 *
 * @v fcpdev            FCP device
 * @v rc                Reason for close
 */
static void fcpdev_close ( struct fcp_device *fcpdev, int rc ) {
        struct fcp_command *fcpcmd;
        struct fcp_command *tmp;

        DBGC ( fcpdev, "FCP %p closed: %s\n", fcpdev, strerror ( rc ) );

        /* Shut down interfaces */
        intf_shutdown ( &fcpdev->scsi, rc );

        /* Shut down any active commands */
        list_for_each_entry_safe ( fcpcmd, tmp, &fcpdev->fcpcmds, list ) {
                fcpcmd_get ( fcpcmd );
                fcpcmd_close ( fcpcmd, rc );
                fcpcmd_put ( fcpcmd );
        }

        /* Drop reference to ULP */
        fc_ulp_detach ( &fcpdev->user );
}

/**
 * Check FCP device flow-control window
 *
 * @v fcpdev            FCP device
 * @ret len             Length of window
 */
static size_t fcpdev_window ( struct fcp_device *fcpdev ) {
        return ( fc_link_ok ( &fcpdev->user.ulp->link ) ?
                 ~( ( size_t ) 0 ) : 0 );
}

/**
 * Describe FCP device using EDD
 *
 * @v fcpdev            FCP device
 * @v type              EDD interface type
 * @v path              EDD device path
 * @ret rc              Return status code
 */
static int fcpdev_edd_describe ( struct fcp_device *fcpdev,
                                 struct edd_interface_type *type,
                                 union edd_device_path *path ) {
        union {
                struct fc_name fc;
                uint64_t u64;
        } wwn;
        union {
                struct scsi_lun scsi;
                uint64_t u64;
        } lun;

        type->type = cpu_to_le64 ( EDD_INTF_TYPE_FIBRE );
        memcpy ( &wwn.fc, &fcpdev->desc.wwn, sizeof ( wwn.fc ) );
        path->fibre.wwn = be64_to_cpu ( wwn.u64 );
        memcpy ( &lun.scsi, &fcpdev->desc.lun, sizeof ( lun.scsi ) );
        path->fibre.lun = be64_to_cpu ( lun.u64 );
        return 0;
}

/**
 * Identify device underlying FCP device
 *
 * @v fcpdev            FCP device
 * @ret device          Underlying device
 */
static struct device * fcpdev_identify_device ( struct fcp_device *fcpdev ) {

        /* We know the underlying device only if the link is up;
         * otherwise we don't have a port to examine.
         */
        if ( ! fc_link_ok ( &fcpdev->user.ulp->link ) ) {
                DBGC ( fcpdev, "FCP %p doesn't know underlying device "
                       "until link is up\n", fcpdev );
                return NULL;
        }

        /* Hand off to port's transport interface */
        assert ( fcpdev->user.ulp->peer->port != NULL );
        return identify_device ( &fcpdev->user.ulp->peer->port->transport );
}

/**
 * Describe as an EFI device path
 *
 * @v fcp               FCP device
 * @ret path            EFI device path, or NULL on error
 */
static EFI_DEVICE_PATH_PROTOCOL *
fcpdev_efi_describe ( struct fcp_device *fcpdev ) {

        return efi_fcp_path ( &fcpdev->desc );
}

/** FCP device SCSI interface operations */
static struct interface_operation fcpdev_scsi_op[] = {
        INTF_OP ( scsi_command, struct fcp_device *, fcpdev_scsi_command ),
        INTF_OP ( xfer_window, struct fcp_device *, fcpdev_window ),
        INTF_OP ( intf_close, struct fcp_device *, fcpdev_close ),
        INTF_OP ( edd_describe, struct fcp_device *, fcpdev_edd_describe ),
        INTF_OP ( identify_device, struct fcp_device *,
                  fcpdev_identify_device ),
        EFI_INTF_OP ( efi_describe, struct fcp_device *, fcpdev_efi_describe ),
};

/** FCP device SCSI interface descriptor */
static struct interface_descriptor fcpdev_scsi_desc =
        INTF_DESC ( struct fcp_device, scsi, fcpdev_scsi_op );

/**
 * Examine FCP ULP link state
 *
 * @v user              Fibre Channel upper-layer protocol user
 */
static void fcpdev_examine ( struct fc_ulp_user *user ) {
        struct fcp_device *fcpdev =
                container_of ( user, struct fcp_device, user );

        if ( fc_link_ok ( &fcpdev->user.ulp->link ) ) {
                DBGC ( fcpdev, "FCP %p link is up\n", fcpdev );
        } else {
                DBGC ( fcpdev, "FCP %p link is down: %s\n",
                       fcpdev, strerror ( fcpdev->user.ulp->link.rc ) );
        }

        /* Notify SCSI layer of window change */
        xfer_window_changed ( &fcpdev->scsi );
}

/**
 * Open FCP device
 *
 * @v parent            Parent interface
 * @v wwn               Fibre Channel WWN
 * @v lun               SCSI LUN
 * @ret rc              Return status code
 */
static int fcpdev_open ( struct interface *parent, struct fc_name *wwn,
                         struct scsi_lun *lun ) {
        struct fc_ulp *ulp;
        struct fcp_device *fcpdev;
        int rc;

        /* Get Fibre Channel ULP interface */
        ulp = fc_ulp_get_wwn_type ( wwn, FC_TYPE_FCP );
        if ( ! ulp ) {
                rc = -ENOMEM;
                goto err_ulp_get;
        }

        /* Allocate and initialise structure */
        fcpdev = zalloc ( sizeof ( *fcpdev ) );
        if ( ! fcpdev ) {
                rc = -ENOMEM;
                goto err_zalloc;
        }
        ref_init ( &fcpdev->refcnt, NULL );
        intf_init ( &fcpdev->scsi, &fcpdev_scsi_desc, &fcpdev->refcnt );
        INIT_LIST_HEAD ( &fcpdev->fcpcmds );
        fc_ulp_user_init ( &fcpdev->user, fcpdev_examine, &fcpdev->refcnt );

        DBGC ( fcpdev, "FCP %p opened for %s\n", fcpdev, fc_ntoa ( wwn ) );

        /* Attach to Fibre Channel ULP */
        fc_ulp_attach ( ulp, &fcpdev->user );

        /* Preserve parameters required for boot firmware table */
        memcpy ( &fcpdev->desc.wwn, wwn, sizeof ( fcpdev->desc.wwn ) );
        memcpy ( &fcpdev->desc.lun, lun, sizeof ( fcpdev->desc.lun ) );

        /* Attach SCSI device to parent interface */
        if ( ( rc = scsi_open ( parent, &fcpdev->scsi, lun ) ) != 0 ) {
                DBGC ( fcpdev, "FCP %p could not create SCSI device: %s\n",
                       fcpdev, strerror ( rc ) );
                goto err_scsi_open;
        }

        /* Drop temporary reference to ULP */
        fc_ulp_put ( ulp );

        /* Mortalise self and return */
        ref_put ( &fcpdev->refcnt );
        return 0;

 err_scsi_open:
        fcpdev_close ( fcpdev, rc );
        ref_put ( &fcpdev->refcnt );
 err_zalloc:
        fc_ulp_put ( ulp );
 err_ulp_get:
        return rc;
}

/******************************************************************************
 *
 * FCP URIs
 *
 ******************************************************************************
 */

/**
 * Parse FCP URI
 *
 * @v uri               URI
 * @ret wwn             Fibre Channel WWN
 * @ret lun             SCSI LUN
 * @ret rc              Return status code
 *
 * An FCP URI has the form "fcp:<wwn>:<lun>" or "fcp://<wwn>/<lun>"
 */
static int fcp_parse_uri ( struct uri *uri, struct fc_name *wwn,
                           struct scsi_lun *lun ) {
        char wwn_buf[ FC_NAME_STRLEN + 1 /* NUL */ ];
        const char *wwn_text;
        const char *lun_text;
        int rc;

        /* Extract WWN and LUN texts from URI */
        if ( uri->opaque ) {
                /* "fcp:<wwn>:<lun>" */
                if ( snprintf ( wwn_buf, sizeof ( wwn_buf ), "%s",
                                uri->opaque ) < ( FC_NAME_STRLEN + 1 /* : */ ) )
                        return -EINVAL;
                if ( uri->opaque[FC_NAME_STRLEN] != ':' )
                        return -EINVAL;
                wwn_text = wwn_buf;
                lun_text = &uri->opaque[FC_NAME_STRLEN + 1];
        } else {
                /* If host exists, path must also exist */
                if ( ! ( uri->host && uri->path ) )
                        return -EINVAL;
                if ( uri->path[0] != '/' )
                        return -EINVAL;
                wwn_text = uri->host;
                lun_text = ( uri->path + 1 );
        }

        /* Parse WWN */
        if ( ( rc = fc_aton ( wwn_text, wwn ) ) != 0 )
                return rc;

        /* Parse LUN */
        if ( ( rc = scsi_parse_lun ( lun_text, lun ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Open FCP URI
 *
 * @v parent            Parent interface
 * @v uri               URI
 * @ret rc              Return status code
 */
static int fcp_open ( struct interface *parent, struct uri *uri ) {
        struct fc_name wwn;
        struct scsi_lun lun;
        int rc;

        /* Parse URI */
        if ( ( rc = fcp_parse_uri ( uri, &wwn, &lun ) ) != 0 )
                return rc;

        /* Open FCP device */
        if ( ( rc = fcpdev_open ( parent, &wwn, &lun ) ) != 0 )
                return rc;

        return 0;
}

/** FCP URI opener */
struct uri_opener fcp_uri_opener __uri_opener = {
        .scheme = "fcp",
        .open = fcp_open,
};