// SPDX-License-Identifier: GPL-2.0
/*
 * driver: reading from and writing to system console on S/390 via SCLP
 *
 * Copyright IBM Corp. 1999, 2009
 *
 * Author(s): Martin Peschke <mpeschke@de.ibm.com>
 *            Martin Schwidefsky <schwidefsky@de.ibm.com>
 */

#include <linux/kmod.h>
#include <linux/types.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/ctype.h>
#include <linux/uaccess.h>

#include "sclp.h"
#include "sclp_rw.h"

/*
 * The room for the SCCB (only for writing) is not equal to a pages size
 * (as it is specified as the maximum size in the SCLP documentation)
 * because of the additional data structure described above.
 */
#define MAX_SCCB_ROOM (PAGE_SIZE - sizeof(struct sclp_buffer))

/* Event type structure for write message and write priority message */
static struct sclp_register sclp_rw_event = {
        .send_mask = EVTYP_MSG_MASK,
};

/*
 * Setup a sclp write buffer. Gets a page as input (4K) and returns
 * a pointer to a struct sclp_buffer structure that is located at the
 * end of the input page. This reduces the buffer space by a few
 * bytes but simplifies things.
 */
struct sclp_buffer *
sclp_make_buffer(void *page, unsigned short columns, unsigned short htab)
{
        struct sclp_buffer *buffer;
        struct sccb_header *sccb;

        sccb = (struct sccb_header *) page;
        /*
         * We keep the struct sclp_buffer structure at the end
         * of the sccb page.
         */
        buffer = ((struct sclp_buffer *) ((addr_t) sccb + PAGE_SIZE)) - 1;
        buffer->sccb = sccb;
        buffer->retry_count = 0;
        buffer->messages = 0;
        buffer->char_sum = 0;
        buffer->current_line = NULL;
        buffer->current_length = 0;
        buffer->columns = columns;
        buffer->htab = htab;

        /* initialize sccb */
        memset(sccb, 0, sizeof(struct sccb_header));
        sccb->length = sizeof(struct sccb_header);

        return buffer;
}

/*
 * Return a pointer to the original page that has been used to create
 * the buffer.
 */
void *
sclp_unmake_buffer(struct sclp_buffer *buffer)
{
        return buffer->sccb;
}

/*
 * Initialize a new message the end of the provided buffer with
 * enough room for max_len characters. Return 0 on success.
 */
static int
sclp_initialize_mto(struct sclp_buffer *buffer, int max_len)
{
        struct sccb_header *sccb;
        struct msg_buf *msg;
        struct mdb *mdb;
        struct go *go;
        struct mto *mto;
        int msg_size;

        /* max size of new message including message text  */
        msg_size = sizeof(struct msg_buf) + max_len;

        /* check if current buffer sccb can contain the mto */
        sccb = buffer->sccb;
        if ((MAX_SCCB_ROOM - sccb->length) < msg_size)
                return -ENOMEM;

        msg = (struct msg_buf *)((addr_t) sccb + sccb->length);
        memset(msg, 0, sizeof(struct msg_buf));
        msg->header.length = sizeof(struct msg_buf);
        msg->header.type = EVTYP_MSG;

        mdb = &msg->mdb;
        mdb->header.length = sizeof(struct mdb);
        mdb->header.type = 1;
        mdb->header.tag = 0xD4C4C240;   /* ebcdic "MDB " */
        mdb->header.revision_code = 1;

        go = &mdb->go;
        go->length = sizeof(struct go);
        go->type = 1;

        mto = &mdb->mto;
        mto->length = sizeof(struct mto);
        mto->type = 4;  /* message text object */
        mto->line_type_flags = LNTPFLGS_ENDTEXT; /* end text */

        /* set pointer to first byte after struct mto. */
        buffer->current_msg = msg;
        buffer->current_line = (char *) (mto + 1);
        buffer->current_length = 0;

        return 0;
}

/*
 * Finalize message initialized by sclp_initialize_mto(),
 * updating the sizes of MTO, enclosing MDB, event buffer and SCCB.
 */
static void
sclp_finalize_mto(struct sclp_buffer *buffer)
{
        struct sccb_header *sccb;
        struct msg_buf *msg;

        /*
         * update values of sizes
         * (SCCB, Event(Message) Buffer, Message Data Block)
         */
        sccb = buffer->sccb;
        msg = buffer->current_msg;
        msg->header.length += buffer->current_length;
        msg->mdb.header.length += buffer->current_length;
        msg->mdb.mto.length += buffer->current_length;
        sccb->length += msg->header.length;

        /*
         * count number of buffered messages (= number of Message Text
         * Objects) and number of buffered characters
         * for the SCCB currently used for buffering and at all
         */
        buffer->messages++;
        buffer->char_sum += buffer->current_length;

        buffer->current_line = NULL;
        buffer->current_length = 0;
        buffer->current_msg = NULL;
}

/*
 * processing of a message including escape characters,
 * returns number of characters written to the output sccb
 * ("processed" means that is not guaranteed that the character have already
 *  been sent to the SCLP but that it will be done at least next time the SCLP
 *  is not busy)
 */
int
sclp_write(struct sclp_buffer *buffer, const unsigned char *msg, int count)
{
        int spaces, i_msg;
        int rc;

        /*
         * parse msg for escape sequences (\t,\v ...) and put formated
         * msg into an mto (created by sclp_initialize_mto).
         *
         * We have to do this work ourselfs because there is no support for
         * these characters on the native machine and only partial support
         * under VM (Why does VM interpret \n but the native machine doesn't ?)
         *
         * Depending on i/o-control setting the message is always written
         * immediately or we wait for a final new line maybe coming with the
         * next message. Besides we avoid a buffer overrun by writing its
         * content.
         *
         * RESTRICTIONS:
         *
         * \r and \b work within one line because we are not able to modify
         * previous output that have already been accepted by the SCLP.
         *
         * \t combined with following \r is not correctly represented because
         * \t is expanded to some spaces but \r does not know about a
         * previous \t and decreases the current position by one column.
         * This is in order to a slim and quick implementation.
         */
        for (i_msg = 0; i_msg < count; i_msg++) {
                switch (msg[i_msg]) {
                case '\n':      /* new line, line feed (ASCII)  */
                        /* check if new mto needs to be created */
                        if (buffer->current_line == NULL) {
                                rc = sclp_initialize_mto(buffer, 0);
                                if (rc)
                                        return i_msg;
                        }
                        sclp_finalize_mto(buffer);
                        break;
                case '\a':      /* bell, one for several times  */
                        /* set SCLP sound alarm bit in General Object */
                        if (buffer->current_line == NULL) {
                                rc = sclp_initialize_mto(buffer,
                                                         buffer->columns);
                                if (rc)
                                        return i_msg;
                        }
                        buffer->current_msg->mdb.go.general_msg_flags |=
                                GNRLMSGFLGS_SNDALRM;
                        break;
                case '\t':      /* horizontal tabulator  */
                        /* check if new mto needs to be created */
                        if (buffer->current_line == NULL) {
                                rc = sclp_initialize_mto(buffer,
                                                         buffer->columns);
                                if (rc)
                                        return i_msg;
                        }
                        /* "go to (next htab-boundary + 1, same line)" */
                        do {
                                if (buffer->current_length >= buffer->columns)
                                        break;
                                /* ok, add a blank */
                                *buffer->current_line++ = 0x40;
                                buffer->current_length++;
                        } while (buffer->current_length % buffer->htab);
                        break;
                case '\f':      /* form feed  */
                case '\v':      /* vertical tabulator  */
                        /* "go to (actual column, actual line + 1)" */
                        /* = new line, leading spaces */
                        if (buffer->current_line != NULL) {
                                spaces = buffer->current_length;
                                sclp_finalize_mto(buffer);
                                rc = sclp_initialize_mto(buffer,
                                                         buffer->columns);
                                if (rc)
                                        return i_msg;
                                memset(buffer->current_line, 0x40, spaces);
                                buffer->current_line += spaces;
                                buffer->current_length = spaces;
                        } else {
                                /* one an empty line this is the same as \n */
                                rc = sclp_initialize_mto(buffer,
                                                         buffer->columns);
                                if (rc)
                                        return i_msg;
                                sclp_finalize_mto(buffer);
                        }
                        break;
                case '\b':      /* backspace  */
                        /* "go to (actual column - 1, actual line)" */
                        /* decrement counter indicating position, */
                        /* do not remove last character */
                        if (buffer->current_line != NULL &&
                            buffer->current_length > 0) {
                                buffer->current_length--;
                                buffer->current_line--;
                        }
                        break;
                case 0x00:      /* end of string  */
                        /* transfer current line to SCCB */
                        if (buffer->current_line != NULL)
                                sclp_finalize_mto(buffer);
                        /* skip the rest of the message including the 0 byte */
                        i_msg = count - 1;
                        break;
                default:        /* no escape character  */
                        /* do not output unprintable characters */
                        if (!isprint(msg[i_msg]))
                                break;
                        /* check if new mto needs to be created */
                        if (buffer->current_line == NULL) {
                                rc = sclp_initialize_mto(buffer,
                                                         buffer->columns);
                                if (rc)
                                        return i_msg;
                        }
                        *buffer->current_line++ = sclp_ascebc(msg[i_msg]);
                        buffer->current_length++;
                        break;
                }
                /* check if current mto is full */
                if (buffer->current_line != NULL &&
                    buffer->current_length >= buffer->columns)
                        sclp_finalize_mto(buffer);
        }

        /* return number of processed characters */
        return i_msg;
}

/*
 * Return the number of free bytes in the sccb
 */
int
sclp_buffer_space(struct sclp_buffer *buffer)
{
        struct sccb_header *sccb;
        int count;

        sccb = buffer->sccb;
        count = MAX_SCCB_ROOM - sccb->length;
        if (buffer->current_line != NULL)
                count -= sizeof(struct msg_buf) + buffer->current_length;
        return count;
}

/*
 * Return number of characters in buffer
 */
unsigned int
sclp_chars_in_buffer(struct sclp_buffer *buffer)
{
        unsigned int count;

        count = buffer->char_sum;
        if (buffer->current_line != NULL)
                count += buffer->current_length;
        return count;
}

/*
 * called by sclp_console_init and/or sclp_tty_init
 */
int
sclp_rw_init(void)
{
        static int init_done = 0;
        int rc;

        if (init_done)
                return 0;

        rc = sclp_register(&sclp_rw_event);
        if (rc == 0)
                init_done = 1;
        return rc;
}

#define SCLP_BUFFER_MAX_RETRY           1

/*
 * second half of Write Event Data-function that has to be done after
 * interruption indicating completion of Service Call.
 */
static void
sclp_writedata_callback(struct sclp_req *request, void *data)
{
        int rc;
        struct sclp_buffer *buffer;
        struct sccb_header *sccb;

        buffer = (struct sclp_buffer *) data;
        sccb = buffer->sccb;

        if (request->status == SCLP_REQ_FAILED) {
                if (buffer->callback != NULL)
                        buffer->callback(buffer, -EIO);
                return;
        }
        /* check SCLP response code and choose suitable action  */
        switch (sccb->response_code) {
        case 0x0020 :
                /* Normal completion, buffer processed, message(s) sent */
                rc = 0;
                break;

        case 0x0340: /* Contained SCLP equipment check */
                if (++buffer->retry_count > SCLP_BUFFER_MAX_RETRY) {
                        rc = -EIO;
                        break;
                }
                /* remove processed buffers and requeue rest */
                if (sclp_remove_processed((struct sccb_header *) sccb) > 0) {
                        /* not all buffers were processed */
                        sccb->response_code = 0x0000;
                        buffer->request.status = SCLP_REQ_FILLED;
                        rc = sclp_add_request(request);
                        if (rc == 0)
                                return;
                } else
                        rc = 0;
                break;

        case 0x0040: /* SCLP equipment check */
        case 0x05f0: /* Target resource in improper state */
                if (++buffer->retry_count > SCLP_BUFFER_MAX_RETRY) {
                        rc = -EIO;
                        break;
                }
                /* retry request */
                sccb->response_code = 0x0000;
                buffer->request.status = SCLP_REQ_FILLED;
                rc = sclp_add_request(request);
                if (rc == 0)
                        return;
                break;
        default:
                if (sccb->response_code == 0x71f0)
                        rc = -ENOMEM;
                else
                        rc = -EINVAL;
                break;
        }
        if (buffer->callback != NULL)
                buffer->callback(buffer, rc);
}

/*
 * Setup the request structure in the struct sclp_buffer to do SCLP Write
 * Event Data and pass the request to the core SCLP loop. Return zero on
 * success, non-zero otherwise.
 */
int
sclp_emit_buffer(struct sclp_buffer *buffer,
                 void (*callback)(struct sclp_buffer *, int))
{
        /* add current line if there is one */
        if (buffer->current_line != NULL)
                sclp_finalize_mto(buffer);

        /* Are there messages in the output buffer ? */
        if (buffer->messages == 0)
                return -EIO;

        buffer->request.command = SCLP_CMDW_WRITE_EVENT_DATA;
        buffer->request.status = SCLP_REQ_FILLED;
        buffer->request.callback = sclp_writedata_callback;
        buffer->request.callback_data = buffer;
        buffer->request.sccb = buffer->sccb;
        buffer->callback = callback;
        return sclp_add_request(&buffer->request);
}