/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *  Copyright (C) 2002 Russell King
 *
 *  Commonly used functions by the ARM SCSI-II drivers.
 */

#include <linux/scatterlist.h>

#define BELT_AND_BRACES

struct arm_cmd_priv {
        struct scsi_pointer scsi_pointer;
};

static inline struct scsi_pointer *arm_scsi_pointer(struct scsi_cmnd *cmd)
{
        struct arm_cmd_priv *acmd = scsi_cmd_priv(cmd);

        return &acmd->scsi_pointer;
}

/*
 * The scatter-gather list handling.  This contains all
 * the yucky stuff that needs to be fixed properly.
 */

/*
 * copy_SCp_to_sg() Assumes contiguous allocation at @sg of at-most @max
 * entries of uninitialized memory. SCp is from scsi-ml and has a valid
 * (possibly chained) sg-list
 */
static inline int copy_SCp_to_sg(struct scatterlist *sg, struct scsi_pointer *SCp, int max)
{
        int bufs = SCp->buffers_residual;

        /* FIXME: It should be easy for drivers to loop on copy_SCp_to_sg().
         * and to remove this BUG_ON. Use min() in-its-place
         */
        BUG_ON(bufs + 1 > max);

        sg_set_buf(sg, SCp->ptr, SCp->this_residual);

        if (bufs) {
                struct scatterlist *src_sg;
                unsigned i;

                for_each_sg(sg_next(SCp->buffer), src_sg, bufs, i)
                        *(++sg) = *src_sg;
                sg_mark_end(sg);
        }

        return bufs + 1;
}

static inline int next_SCp(struct scsi_pointer *SCp)
{
        int ret = SCp->buffers_residual;
        if (ret) {
                SCp->buffer = sg_next(SCp->buffer);
                SCp->buffers_residual--;
                SCp->ptr = sg_virt(SCp->buffer);
                SCp->this_residual = SCp->buffer->length;
        } else {
                SCp->ptr = NULL;
                SCp->this_residual = 0;
        }
        return ret;
}

static inline unsigned char get_next_SCp_byte(struct scsi_pointer *SCp)
{
        char c = *SCp->ptr;

        SCp->ptr += 1;
        SCp->this_residual -= 1;

        return c;
}

static inline void put_next_SCp_byte(struct scsi_pointer *SCp, unsigned char c)
{
        *SCp->ptr = c;
        SCp->ptr += 1;
        SCp->this_residual -= 1;
}

static inline void init_SCp(struct scsi_cmnd *SCpnt)
{
        struct scsi_pointer *scsi_pointer = arm_scsi_pointer(SCpnt);

        memset(scsi_pointer, 0, sizeof(struct scsi_pointer));

        if (scsi_bufflen(SCpnt)) {
                unsigned long len = 0;

                scsi_pointer->buffer = scsi_sglist(SCpnt);
                scsi_pointer->buffers_residual = scsi_sg_count(SCpnt) - 1;
                scsi_pointer->ptr = sg_virt(scsi_pointer->buffer);
                scsi_pointer->this_residual = scsi_pointer->buffer->length;
                scsi_pointer->phase = scsi_bufflen(SCpnt);

#ifdef BELT_AND_BRACES
                {       /*
                         * Calculate correct buffer length.  Some commands
                         * come in with the wrong scsi_bufflen.
                         */
                        struct scatterlist *sg;
                        unsigned i, sg_count = scsi_sg_count(SCpnt);

                        scsi_for_each_sg(SCpnt, sg, sg_count, i)
                                len += sg->length;

                        if (scsi_bufflen(SCpnt) != len) {
                                printk(KERN_WARNING
                                       "scsi%d.%c: bad request buffer "
                                       "length %d, should be %ld\n",
                                        SCpnt->device->host->host_no,
                                        '0' + SCpnt->device->id,
                                        scsi_bufflen(SCpnt), len);
                                /*
                                 * FIXME: Totaly naive fixup. We should abort
                                 * with error
                                 */
                                scsi_pointer->phase =
                                        min_t(unsigned long, len,
                                              scsi_bufflen(SCpnt));
                        }
                }
#endif
        } else {
                scsi_pointer->ptr = NULL;
                scsi_pointer->this_residual = 0;
                scsi_pointer->phase = 0;
        }
}