// SPDX-License-Identifier: GPL-2.0-only
/*
 *
 *  Copyright (C) 2005 Mike Isely <isely@pobox.com>
 */

#include "pvrusb2-ioread.h"
#include "pvrusb2-debug.h"
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/uaccess.h>

#define BUFFER_COUNT 32
#define BUFFER_SIZE PAGE_ALIGN(0x4000)

struct pvr2_ioread {
        struct pvr2_stream *stream;
        char *buffer_storage[BUFFER_COUNT];
        char *sync_key_ptr;
        unsigned int sync_key_len;
        unsigned int sync_buf_offs;
        unsigned int sync_state;
        unsigned int sync_trashed_count;
        int enabled;         // Streaming is on
        int spigot_open;     // OK to pass data to client
        int stream_running;  // Passing data to client now

        /* State relevant to current buffer being read */
        struct pvr2_buffer *c_buf;
        char *c_data_ptr;
        unsigned int c_data_len;
        unsigned int c_data_offs;
        struct mutex mutex;
};

static int pvr2_ioread_init(struct pvr2_ioread *cp)
{
        unsigned int idx;

        cp->stream = NULL;
        mutex_init(&cp->mutex);

        for (idx = 0; idx < BUFFER_COUNT; idx++) {
                cp->buffer_storage[idx] = kmalloc(BUFFER_SIZE,GFP_KERNEL);
                if (!(cp->buffer_storage[idx])) break;
        }

        if (idx < BUFFER_COUNT) {
                // An allocation appears to have failed
                for (idx = 0; idx < BUFFER_COUNT; idx++) {
                        if (!(cp->buffer_storage[idx])) continue;
                        kfree(cp->buffer_storage[idx]);
                }
                return -ENOMEM;
        }
        return 0;
}

static void pvr2_ioread_done(struct pvr2_ioread *cp)
{
        unsigned int idx;

        pvr2_ioread_setup(cp,NULL);
        for (idx = 0; idx < BUFFER_COUNT; idx++) {
                if (!(cp->buffer_storage[idx])) continue;
                kfree(cp->buffer_storage[idx]);
        }
}

struct pvr2_ioread *pvr2_ioread_create(void)
{
        struct pvr2_ioread *cp;
        cp = kzalloc_obj(*cp);
        if (!cp) return NULL;
        pvr2_trace(PVR2_TRACE_STRUCT,"pvr2_ioread_create id=%p",cp);
        if (pvr2_ioread_init(cp) < 0) {
                kfree(cp);
                return NULL;
        }
        return cp;
}

void pvr2_ioread_destroy(struct pvr2_ioread *cp)
{
        if (!cp) return;
        pvr2_ioread_done(cp);
        pvr2_trace(PVR2_TRACE_STRUCT,"pvr2_ioread_destroy id=%p",cp);
        if (cp->sync_key_ptr) {
                kfree(cp->sync_key_ptr);
                cp->sync_key_ptr = NULL;
        }
        kfree(cp);
}

void pvr2_ioread_set_sync_key(struct pvr2_ioread *cp,
                              const char *sync_key_ptr,
                              unsigned int sync_key_len)
{
        if (!cp) return;

        if (!sync_key_ptr) sync_key_len = 0;
        if ((sync_key_len == cp->sync_key_len) &&
            ((!sync_key_len) ||
             (!memcmp(sync_key_ptr,cp->sync_key_ptr,sync_key_len)))) return;

        if (sync_key_len != cp->sync_key_len) {
                if (cp->sync_key_ptr) {
                        kfree(cp->sync_key_ptr);
                        cp->sync_key_ptr = NULL;
                }
                cp->sync_key_len = 0;
                if (sync_key_len) {
                        cp->sync_key_ptr = kmalloc(sync_key_len,GFP_KERNEL);
                        if (cp->sync_key_ptr) {
                                cp->sync_key_len = sync_key_len;
                        }
                }
        }
        if (!cp->sync_key_len) return;
        memcpy(cp->sync_key_ptr,sync_key_ptr,cp->sync_key_len);
}

static void pvr2_ioread_stop(struct pvr2_ioread *cp)
{
        if (!(cp->enabled)) return;
        pvr2_trace(PVR2_TRACE_START_STOP,
                   "/*---TRACE_READ---*/ pvr2_ioread_stop id=%p",cp);
        pvr2_stream_kill(cp->stream);
        cp->c_buf = NULL;
        cp->c_data_ptr = NULL;
        cp->c_data_len = 0;
        cp->c_data_offs = 0;
        cp->enabled = 0;
        cp->stream_running = 0;
        cp->spigot_open = 0;
        if (cp->sync_state) {
                pvr2_trace(PVR2_TRACE_DATA_FLOW,
                           "/*---TRACE_READ---*/ sync_state <== 0");
                cp->sync_state = 0;
        }
}

static int pvr2_ioread_start(struct pvr2_ioread *cp)
{
        int stat;
        struct pvr2_buffer *bp;
        if (cp->enabled) return 0;
        if (!(cp->stream)) return 0;
        pvr2_trace(PVR2_TRACE_START_STOP,
                   "/*---TRACE_READ---*/ pvr2_ioread_start id=%p",cp);
        while ((bp = pvr2_stream_get_idle_buffer(cp->stream)) != NULL) {
                stat = pvr2_buffer_queue(bp);
                if (stat < 0) {
                        pvr2_trace(PVR2_TRACE_DATA_FLOW,
                                   "/*---TRACE_READ---*/ pvr2_ioread_start id=%p error=%d",
                                   cp,stat);
                        pvr2_ioread_stop(cp);
                        return stat;
                }
        }
        cp->enabled = !0;
        cp->c_buf = NULL;
        cp->c_data_ptr = NULL;
        cp->c_data_len = 0;
        cp->c_data_offs = 0;
        cp->stream_running = 0;
        if (cp->sync_key_len) {
                pvr2_trace(PVR2_TRACE_DATA_FLOW,
                           "/*---TRACE_READ---*/ sync_state <== 1");
                cp->sync_state = 1;
                cp->sync_trashed_count = 0;
                cp->sync_buf_offs = 0;
        }
        cp->spigot_open = 0;
        return 0;
}

struct pvr2_stream *pvr2_ioread_get_stream(struct pvr2_ioread *cp)
{
        return cp->stream;
}

int pvr2_ioread_setup(struct pvr2_ioread *cp,struct pvr2_stream *sp)
{
        int ret;
        unsigned int idx;
        struct pvr2_buffer *bp;

        mutex_lock(&cp->mutex);
        do {
                if (cp->stream) {
                        pvr2_trace(PVR2_TRACE_START_STOP,
                                   "/*---TRACE_READ---*/ pvr2_ioread_setup (tear-down) id=%p",
                                   cp);
                        pvr2_ioread_stop(cp);
                        pvr2_stream_kill(cp->stream);
                        if (pvr2_stream_get_buffer_count(cp->stream)) {
                                pvr2_stream_set_buffer_count(cp->stream,0);
                        }
                        cp->stream = NULL;
                }
                if (sp) {
                        pvr2_trace(PVR2_TRACE_START_STOP,
                                   "/*---TRACE_READ---*/ pvr2_ioread_setup (setup) id=%p",
                                   cp);
                        pvr2_stream_kill(sp);
                        ret = pvr2_stream_set_buffer_count(sp,BUFFER_COUNT);
                        if (ret < 0) {
                                mutex_unlock(&cp->mutex);
                                return ret;
                        }
                        for (idx = 0; idx < BUFFER_COUNT; idx++) {
                                bp = pvr2_stream_get_buffer(sp,idx);
                                pvr2_buffer_set_buffer(bp,
                                                       cp->buffer_storage[idx],
                                                       BUFFER_SIZE);
                        }
                        cp->stream = sp;
                }
        } while (0);
        mutex_unlock(&cp->mutex);

        return 0;
}

int pvr2_ioread_set_enabled(struct pvr2_ioread *cp,int fl)
{
        int ret = 0;
        if ((!fl) == (!(cp->enabled))) return ret;

        mutex_lock(&cp->mutex);
        do {
                if (fl) {
                        ret = pvr2_ioread_start(cp);
                } else {
                        pvr2_ioread_stop(cp);
                }
        } while (0);
        mutex_unlock(&cp->mutex);
        return ret;
}

static int pvr2_ioread_get_buffer(struct pvr2_ioread *cp)
{
        int stat;

        while (cp->c_data_len <= cp->c_data_offs) {
                if (cp->c_buf) {
                        // Flush out current buffer first.
                        stat = pvr2_buffer_queue(cp->c_buf);
                        if (stat < 0) {
                                // Streaming error...
                                pvr2_trace(PVR2_TRACE_DATA_FLOW,
                                           "/*---TRACE_READ---*/ pvr2_ioread_read id=%p queue_error=%d",
                                           cp,stat);
                                pvr2_ioread_stop(cp);
                                return 0;
                        }
                        cp->c_buf = NULL;
                        cp->c_data_ptr = NULL;
                        cp->c_data_len = 0;
                        cp->c_data_offs = 0;
                }
                // Now get a freshly filled buffer.
                cp->c_buf = pvr2_stream_get_ready_buffer(cp->stream);
                if (!cp->c_buf) break; // Nothing ready; done.
                cp->c_data_len = pvr2_buffer_get_count(cp->c_buf);
                if (!cp->c_data_len) {
                        // Nothing transferred.  Was there an error?
                        stat = pvr2_buffer_get_status(cp->c_buf);
                        if (stat < 0) {
                                // Streaming error...
                                pvr2_trace(PVR2_TRACE_DATA_FLOW,
                                           "/*---TRACE_READ---*/ pvr2_ioread_read id=%p buffer_error=%d",
                                           cp,stat);
                                pvr2_ioread_stop(cp);
                                // Give up.
                                return 0;
                        }
                        // Start over...
                        continue;
                }
                cp->c_data_offs = 0;
                cp->c_data_ptr = cp->buffer_storage[
                        pvr2_buffer_get_id(cp->c_buf)];
        }
        return !0;
}

static void pvr2_ioread_filter(struct pvr2_ioread *cp)
{
        unsigned int idx;
        if (!cp->enabled) return;
        if (cp->sync_state != 1) return;

        // Search the stream for our synchronization key.  This is made
        // complicated by the fact that in order to be honest with
        // ourselves here we must search across buffer boundaries...
        mutex_lock(&cp->mutex);
        while (1) {
                // Ensure we have a buffer
                if (!pvr2_ioread_get_buffer(cp)) break;
                if (!cp->c_data_len) break;

                // Now walk the buffer contents until we match the key or
                // run out of buffer data.
                for (idx = cp->c_data_offs; idx < cp->c_data_len; idx++) {
                        if (cp->sync_buf_offs >= cp->sync_key_len) break;
                        if (cp->c_data_ptr[idx] ==
                            cp->sync_key_ptr[cp->sync_buf_offs]) {
                                // Found the next key byte
                                (cp->sync_buf_offs)++;
                        } else {
                                // Whoops, mismatched.  Start key over...
                                cp->sync_buf_offs = 0;
                        }
                }

                // Consume what we've walked through
                cp->c_data_offs += idx;
                cp->sync_trashed_count += idx;

                // If we've found the key, then update state and get out.
                if (cp->sync_buf_offs >= cp->sync_key_len) {
                        cp->sync_trashed_count -= cp->sync_key_len;
                        pvr2_trace(PVR2_TRACE_DATA_FLOW,
                                   "/*---TRACE_READ---*/ sync_state <== 2 (skipped %u bytes)",
                                   cp->sync_trashed_count);
                        cp->sync_state = 2;
                        cp->sync_buf_offs = 0;
                        break;
                }

                if (cp->c_data_offs < cp->c_data_len) {
                        // Sanity check - should NEVER get here
                        pvr2_trace(PVR2_TRACE_ERROR_LEGS,
                                   "ERROR: pvr2_ioread filter sync problem len=%u offs=%u",
                                   cp->c_data_len,cp->c_data_offs);
                        // Get out so we don't get stuck in an infinite
                        // loop.
                        break;
                }

                continue; // (for clarity)
        }
        mutex_unlock(&cp->mutex);
}

int pvr2_ioread_avail(struct pvr2_ioread *cp)
{
        int ret;
        if (!(cp->enabled)) {
                // Stream is not enabled; so this is an I/O error
                return -EIO;
        }

        if (cp->sync_state == 1) {
                pvr2_ioread_filter(cp);
                if (cp->sync_state == 1) return -EAGAIN;
        }

        ret = 0;
        if (cp->stream_running) {
                if (!pvr2_stream_get_ready_count(cp->stream)) {
                        // No data available at all right now.
                        ret = -EAGAIN;
                }
        } else {
                if (pvr2_stream_get_ready_count(cp->stream) < BUFFER_COUNT/2) {
                        // Haven't buffered up enough yet; try again later
                        ret = -EAGAIN;
                }
        }

        if ((!(cp->spigot_open)) != (!(ret == 0))) {
                cp->spigot_open = (ret == 0);
                pvr2_trace(PVR2_TRACE_DATA_FLOW,
                           "/*---TRACE_READ---*/ data is %s",
                           cp->spigot_open ? "available" : "pending");
        }

        return ret;
}

int pvr2_ioread_read(struct pvr2_ioread *cp,void __user *buf,unsigned int cnt)
{
        unsigned int copied_cnt;
        unsigned int bcnt;
        const char *src;
        int stat;
        int ret = 0;
        unsigned int req_cnt = cnt;

        if (!cnt) {
                pvr2_trace(PVR2_TRACE_TRAP,
                           "/*---TRACE_READ---*/ pvr2_ioread_read id=%p ZERO Request? Returning zero.",
cp);
                return 0;
        }

        stat = pvr2_ioread_avail(cp);
        if (stat < 0) return stat;

        cp->stream_running = !0;

        mutex_lock(&cp->mutex);
        do {

                // Suck data out of the buffers and copy to the user
                copied_cnt = 0;
                if (!buf) cnt = 0;
                while (1) {
                        if (!pvr2_ioread_get_buffer(cp)) {
                                ret = -EIO;
                                break;
                        }

                        if (!cnt) break;

                        if (cp->sync_state == 2) {
                                // We're repeating the sync key data into
                                // the stream.
                                src = cp->sync_key_ptr + cp->sync_buf_offs;
                                bcnt = cp->sync_key_len - cp->sync_buf_offs;
                        } else {
                                // Normal buffer copy
                                src = cp->c_data_ptr + cp->c_data_offs;
                                bcnt = cp->c_data_len - cp->c_data_offs;
                        }

                        if (!bcnt) break;

                        // Don't run past user's buffer
                        if (bcnt > cnt) bcnt = cnt;

                        if (copy_to_user(buf,src,bcnt)) {
                                // User supplied a bad pointer?
                                // Give up - this *will* cause data
                                // to be lost.
                                ret = -EFAULT;
                                break;
                        }
                        cnt -= bcnt;
                        buf += bcnt;
                        copied_cnt += bcnt;

                        if (cp->sync_state == 2) {
                                // Update offset inside sync key that we're
                                // repeating back out.
                                cp->sync_buf_offs += bcnt;
                                if (cp->sync_buf_offs >= cp->sync_key_len) {
                                        // Consumed entire key; switch mode
                                        // to normal.
                                        pvr2_trace(PVR2_TRACE_DATA_FLOW,
                                                   "/*---TRACE_READ---*/ sync_state <== 0");
                                        cp->sync_state = 0;
                                }
                        } else {
                                // Update buffer offset.
                                cp->c_data_offs += bcnt;
                        }
                }

        } while (0);
        mutex_unlock(&cp->mutex);

        if (!ret) {
                if (copied_cnt) {
                        // If anything was copied, return that count
                        ret = copied_cnt;
                } else {
                        // Nothing copied; suggest to caller that another
                        // attempt should be tried again later
                        ret = -EAGAIN;
                }
        }

        pvr2_trace(PVR2_TRACE_DATA_FLOW,
                   "/*---TRACE_READ---*/ pvr2_ioread_read id=%p request=%d result=%d",
                   cp,req_cnt,ret);
        return ret;
}