// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  BSG helper library
 *
 *  Copyright (C) 2008   James Smart, Emulex Corporation
 *  Copyright (C) 2011   Red Hat, Inc.  All rights reserved.
 *  Copyright (C) 2011   Mike Christie
 */
#include <linux/slab.h>
#include <linux/blk-mq.h>
#include <linux/delay.h>
#include <linux/scatterlist.h>
#include <linux/bsg-lib.h>
#include <linux/export.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/sg.h>

#define uptr64(val) ((void __user *)(uintptr_t)(val))

struct bsg_set {
        struct blk_mq_tag_set   tag_set;
        bsg_job_fn              *job_fn;
        bsg_timeout_fn          *timeout_fn;
};

static int bsg_transport_check_proto(struct sg_io_v4 *hdr)
{
        if (hdr->protocol != BSG_PROTOCOL_SCSI  ||
            hdr->subprotocol != BSG_SUB_PROTOCOL_SCSI_TRANSPORT)
                return -EINVAL;
        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;
        return 0;
}

static int bsg_transport_fill_hdr(struct request *rq, struct sg_io_v4 *hdr,
                fmode_t mode)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(rq);
        int ret;

        job->request_len = hdr->request_len;
        job->request = memdup_user(uptr64(hdr->request), hdr->request_len);
        if (IS_ERR(job->request))
                return PTR_ERR(job->request);

        if (hdr->dout_xfer_len && hdr->din_xfer_len) {
                job->bidi_rq = blk_get_request(rq->q, REQ_OP_SCSI_IN, 0);
                if (IS_ERR(job->bidi_rq)) {
                        ret = PTR_ERR(job->bidi_rq);
                        goto out;
                }

                ret = blk_rq_map_user(rq->q, job->bidi_rq, NULL,
                                uptr64(hdr->din_xferp), hdr->din_xfer_len,
                                GFP_KERNEL);
                if (ret)
                        goto out_free_bidi_rq;

                job->bidi_bio = job->bidi_rq->bio;
        } else {
                job->bidi_rq = NULL;
                job->bidi_bio = NULL;
        }

        return 0;

out_free_bidi_rq:
        if (job->bidi_rq)
                blk_put_request(job->bidi_rq);
out:
        kfree(job->request);
        return ret;
}

static int bsg_transport_complete_rq(struct request *rq, struct sg_io_v4 *hdr)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(rq);
        int ret = 0;

        /*
         * The assignments below don't make much sense, but are kept for
         * bug by bug backwards compatibility:
         */
        hdr->device_status = job->result & 0xff;
        hdr->transport_status = host_byte(job->result);
        hdr->driver_status = driver_byte(job->result);
        hdr->info = 0;
        if (hdr->device_status || hdr->transport_status || hdr->driver_status)
                hdr->info |= SG_INFO_CHECK;
        hdr->response_len = 0;

        if (job->result < 0) {
                /* we're only returning the result field in the reply */
                job->reply_len = sizeof(u32);
                ret = job->result;
        }

        if (job->reply_len && hdr->response) {
                int len = min(hdr->max_response_len, job->reply_len);

                if (copy_to_user(uptr64(hdr->response), job->reply, len))
                        ret = -EFAULT;
                else
                        hdr->response_len = len;
        }

        /* we assume all request payload was transferred, residual == 0 */
        hdr->dout_resid = 0;

        if (job->bidi_rq) {
                unsigned int rsp_len = job->reply_payload.payload_len;

                if (WARN_ON(job->reply_payload_rcv_len > rsp_len))
                        hdr->din_resid = 0;
                else
                        hdr->din_resid = rsp_len - job->reply_payload_rcv_len;
        } else {
                hdr->din_resid = 0;
        }

        return ret;
}

static void bsg_transport_free_rq(struct request *rq)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(rq);

        if (job->bidi_rq) {
                blk_rq_unmap_user(job->bidi_bio);
                blk_put_request(job->bidi_rq);
        }

        kfree(job->request);
}

static const struct bsg_ops bsg_transport_ops = {
        .check_proto            = bsg_transport_check_proto,
        .fill_hdr               = bsg_transport_fill_hdr,
        .complete_rq            = bsg_transport_complete_rq,
        .free_rq                = bsg_transport_free_rq,
};

/**
 * bsg_teardown_job - routine to teardown a bsg job
 * @kref: kref inside bsg_job that is to be torn down
 */
static void bsg_teardown_job(struct kref *kref)
{
        struct bsg_job *job = container_of(kref, struct bsg_job, kref);
        struct request *rq = blk_mq_rq_from_pdu(job);

        put_device(job->dev);   /* release reference for the request */

        kfree(job->request_payload.sg_list);
        kfree(job->reply_payload.sg_list);

        blk_mq_end_request(rq, BLK_STS_OK);
}

void bsg_job_put(struct bsg_job *job)
{
        kref_put(&job->kref, bsg_teardown_job);
}
EXPORT_SYMBOL_GPL(bsg_job_put);

int bsg_job_get(struct bsg_job *job)
{
        return kref_get_unless_zero(&job->kref);
}
EXPORT_SYMBOL_GPL(bsg_job_get);

/**
 * bsg_job_done - completion routine for bsg requests
 * @job: bsg_job that is complete
 * @result: job reply result
 * @reply_payload_rcv_len: length of payload recvd
 *
 * The LLD should call this when the bsg job has completed.
 */
void bsg_job_done(struct bsg_job *job, int result,
                  unsigned int reply_payload_rcv_len)
{
        job->result = result;
        job->reply_payload_rcv_len = reply_payload_rcv_len;
        blk_mq_complete_request(blk_mq_rq_from_pdu(job));
}
EXPORT_SYMBOL_GPL(bsg_job_done);

/**
 * bsg_complete - softirq done routine for destroying the bsg requests
 * @rq: BSG request that holds the job to be destroyed
 */
static void bsg_complete(struct request *rq)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(rq);

        bsg_job_put(job);
}

static int bsg_map_buffer(struct bsg_buffer *buf, struct request *req)
{
        size_t sz = (sizeof(struct scatterlist) * req->nr_phys_segments);

        BUG_ON(!req->nr_phys_segments);

        buf->sg_list = kzalloc(sz, GFP_KERNEL);
        if (!buf->sg_list)
                return -ENOMEM;
        sg_init_table(buf->sg_list, req->nr_phys_segments);
        buf->sg_cnt = blk_rq_map_sg(req->q, req, buf->sg_list);
        buf->payload_len = blk_rq_bytes(req);
        return 0;
}

/**
 * bsg_prepare_job - create the bsg_job structure for the bsg request
 * @dev: device that is being sent the bsg request
 * @req: BSG request that needs a job structure
 */
static bool bsg_prepare_job(struct device *dev, struct request *req)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(req);
        int ret;

        job->timeout = req->timeout;

        if (req->bio) {
                ret = bsg_map_buffer(&job->request_payload, req);
                if (ret)
                        goto failjob_rls_job;
        }
        if (job->bidi_rq) {
                ret = bsg_map_buffer(&job->reply_payload, job->bidi_rq);
                if (ret)
                        goto failjob_rls_rqst_payload;
        }
        job->dev = dev;
        /* take a reference for the request */
        get_device(job->dev);
        kref_init(&job->kref);
        return true;

failjob_rls_rqst_payload:
        kfree(job->request_payload.sg_list);
failjob_rls_job:
        job->result = -ENOMEM;
        return false;
}

/**
 * bsg_queue_rq - generic handler for bsg requests
 * @hctx: hardware queue
 * @bd: queue data
 *
 * On error the create_bsg_job function should return a -Exyz error value
 * that will be set to ->result.
 *
 * Drivers/subsys should pass this to the queue init function.
 */
static blk_status_t bsg_queue_rq(struct blk_mq_hw_ctx *hctx,
                                 const struct blk_mq_queue_data *bd)
{
        struct request_queue *q = hctx->queue;
        struct device *dev = q->queuedata;
        struct request *req = bd->rq;
        struct bsg_set *bset =
                container_of(q->tag_set, struct bsg_set, tag_set);
        int sts = BLK_STS_IOERR;
        int ret;

        blk_mq_start_request(req);

        if (!get_device(dev))
                return BLK_STS_IOERR;

        if (!bsg_prepare_job(dev, req))
                goto out;

        ret = bset->job_fn(blk_mq_rq_to_pdu(req));
        if (!ret)
                sts = BLK_STS_OK;

out:
        put_device(dev);
        return sts;
}

/* called right after the request is allocated for the request_queue */
static int bsg_init_rq(struct blk_mq_tag_set *set, struct request *req,
                       unsigned int hctx_idx, unsigned int numa_node)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(req);

        job->reply = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_KERNEL);
        if (!job->reply)
                return -ENOMEM;
        return 0;
}

/* called right before the request is given to the request_queue user */
static void bsg_initialize_rq(struct request *req)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(req);
        void *reply = job->reply;

        memset(job, 0, sizeof(*job));
        job->reply = reply;
        job->reply_len = SCSI_SENSE_BUFFERSIZE;
        job->dd_data = job + 1;
}

static void bsg_exit_rq(struct blk_mq_tag_set *set, struct request *req,
                       unsigned int hctx_idx)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(req);

        kfree(job->reply);
}

void bsg_remove_queue(struct request_queue *q)
{
        if (q) {
                struct bsg_set *bset =
                        container_of(q->tag_set, struct bsg_set, tag_set);

                bsg_unregister_queue(q);
                blk_cleanup_queue(q);
                blk_mq_free_tag_set(&bset->tag_set);
                kfree(bset);
        }
}
EXPORT_SYMBOL_GPL(bsg_remove_queue);

static enum blk_eh_timer_return bsg_timeout(struct request *rq, bool reserved)
{
        struct bsg_set *bset =
                container_of(rq->q->tag_set, struct bsg_set, tag_set);

        if (!bset->timeout_fn)
                return BLK_EH_DONE;
        return bset->timeout_fn(rq);
}

static const struct blk_mq_ops bsg_mq_ops = {
        .queue_rq               = bsg_queue_rq,
        .init_request           = bsg_init_rq,
        .exit_request           = bsg_exit_rq,
        .initialize_rq_fn       = bsg_initialize_rq,
        .complete               = bsg_complete,
        .timeout                = bsg_timeout,
};

/**
 * bsg_setup_queue - Create and add the bsg hooks so we can receive requests
 * @dev: device to attach bsg device to
 * @name: device to give bsg device
 * @job_fn: bsg job handler
 * @timeout: timeout handler function pointer
 * @dd_job_size: size of LLD data needed for each job
 */
struct request_queue *bsg_setup_queue(struct device *dev, const char *name,
                bsg_job_fn *job_fn, bsg_timeout_fn *timeout, int dd_job_size)
{
        struct bsg_set *bset;
        struct blk_mq_tag_set *set;
        struct request_queue *q;
        int ret = -ENOMEM;

        bset = kzalloc(sizeof(*bset), GFP_KERNEL);
        if (!bset)
                return ERR_PTR(-ENOMEM);

        bset->job_fn = job_fn;
        bset->timeout_fn = timeout;

        set = &bset->tag_set;
        set->ops = &bsg_mq_ops,
        set->nr_hw_queues = 1;
        set->queue_depth = 128;
        set->numa_node = NUMA_NO_NODE;
        set->cmd_size = sizeof(struct bsg_job) + dd_job_size;
        set->flags = BLK_MQ_F_NO_SCHED | BLK_MQ_F_BLOCKING;
        if (blk_mq_alloc_tag_set(set))
                goto out_tag_set;

        q = blk_mq_init_queue(set);
        if (IS_ERR(q)) {
                ret = PTR_ERR(q);
                goto out_queue;
        }

        q->queuedata = dev;
        blk_queue_rq_timeout(q, BLK_DEFAULT_SG_TIMEOUT);

        ret = bsg_register_queue(q, dev, name, &bsg_transport_ops);
        if (ret) {
                printk(KERN_ERR "%s: bsg interface failed to "
                       "initialize - register queue\n", dev->kobj.name);
                goto out_cleanup_queue;
        }

        return q;
out_cleanup_queue:
        blk_cleanup_queue(q);
out_queue:
        blk_mq_free_tag_set(set);
out_tag_set:
        kfree(bset);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(bsg_setup_queue);