/*
 * Copyright 2012 Cisco Systems, Inc.  All rights reserved.
 *
 * This program is free software; you may redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/debugfs.h>
#include "fnic.h"

static struct dentry *fnic_trace_debugfs_root;
static struct dentry *fnic_trace_debugfs_file;
static struct dentry *fnic_trace_enable;

/*
 * fnic_trace_ctrl_open - Open the trace_enable file
 * @inode: The inode pointer.
 * @file: The file pointer to attach the trace enable/disable flag.
 *
 * Description:
 * This routine opens a debugsfs file trace_enable.
 *
 * Returns:
 * This function returns zero if successful.
 */
static int fnic_trace_ctrl_open(struct inode *inode, struct file *filp)
{
        filp->private_data = inode->i_private;
        return 0;
}

/*
 * fnic_trace_ctrl_read - Read a trace_enable debugfs file
 * @filp: The file pointer to read from.
 * @ubuf: The buffer to copy the data to.
 * @cnt: The number of bytes to read.
 * @ppos: The position in the file to start reading from.
 *
 * Description:
 * This routine reads value of variable fnic_tracing_enabled
 * and stores into local @buf. It will start reading file at @ppos and
 * copy up to @cnt of data to @ubuf from @buf.
 *
 * Returns:
 * This function returns the amount of data that was read.
 */
static ssize_t fnic_trace_ctrl_read(struct file *filp,
                                  char __user *ubuf,
                                  size_t cnt, loff_t *ppos)
{
        char buf[64];
        int len;
        len = sprintf(buf, "%u\n", fnic_tracing_enabled);

        return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
}

/*
 * fnic_trace_ctrl_write - Write to trace_enable debugfs file
 * @filp: The file pointer to write from.
 * @ubuf: The buffer to copy the data from.
 * @cnt: The number of bytes to write.
 * @ppos: The position in the file to start writing to.
 *
 * Description:
 * This routine writes data from user buffer @ubuf to buffer @buf and
 * sets fnic_tracing_enabled value as per user input.
 *
 * Returns:
 * This function returns the amount of data that was written.
 */
static ssize_t fnic_trace_ctrl_write(struct file *filp,
                                  const char __user *ubuf,
                                  size_t cnt, loff_t *ppos)
{
        char buf[64];
        unsigned long val;
        int ret;

        if (cnt >= sizeof(buf))
                return -EINVAL;

        if (copy_from_user(&buf, ubuf, cnt))
                return -EFAULT;

        buf[cnt] = 0;

        ret = kstrtoul(buf, 10, &val);
        if (ret < 0)
                return ret;

        fnic_tracing_enabled = val;
        (*ppos)++;

        return cnt;
}

/*
 * fnic_trace_debugfs_open - Open the fnic trace log
 * @inode: The inode pointer
 * @file: The file pointer to attach the log output
 *
 * Description:
 * This routine is the entry point for the debugfs open file operation.
 * It allocates the necessary buffer for the log, fills the buffer from
 * the in-memory log and then returns a pointer to that log in
 * the private_data field in @file.
 *
 * Returns:
 * This function returns zero if successful. On error it will return
 * a negative error value.
 */
static int fnic_trace_debugfs_open(struct inode *inode,
                                  struct file *file)
{
        fnic_dbgfs_t *fnic_dbg_prt;
        fnic_dbg_prt = kzalloc(sizeof(fnic_dbgfs_t), GFP_KERNEL);
        if (!fnic_dbg_prt)
                return -ENOMEM;

        fnic_dbg_prt->buffer = vmalloc((3*(trace_max_pages * PAGE_SIZE)));
        if (!fnic_dbg_prt->buffer) {
                kfree(fnic_dbg_prt);
                return -ENOMEM;
        }
        memset((void *)fnic_dbg_prt->buffer, 0,
                          (3*(trace_max_pages * PAGE_SIZE)));
        fnic_dbg_prt->buffer_len = fnic_get_trace_data(fnic_dbg_prt);
        file->private_data = fnic_dbg_prt;
        return 0;
}

/*
 * fnic_trace_debugfs_lseek - Seek through a debugfs file
 * @file: The file pointer to seek through.
 * @offset: The offset to seek to or the amount to seek by.
 * @howto: Indicates how to seek.
 *
 * Description:
 * This routine is the entry point for the debugfs lseek file operation.
 * The @howto parameter indicates whether @offset is the offset to directly
 * seek to, or if it is a value to seek forward or reverse by. This function
 * figures out what the new offset of the debugfs file will be and assigns
 * that value to the f_pos field of @file.
 *
 * Returns:
 * This function returns the new offset if successful and returns a negative
 * error if unable to process the seek.
 */
static loff_t fnic_trace_debugfs_lseek(struct file *file,
                                        loff_t offset,
                                        int howto)
{
        fnic_dbgfs_t *fnic_dbg_prt = file->private_data;
        return fixed_size_llseek(file, offset, howto,
                                fnic_dbg_prt->buffer_len);
}

/*
 * fnic_trace_debugfs_read - Read a debugfs file
 * @file: The file pointer to read from.
 * @ubuf: The buffer to copy the data to.
 * @nbytes: The number of bytes to read.
 * @pos: The position in the file to start reading from.
 *
 * Description:
 * This routine reads data from the buffer indicated in the private_data
 * field of @file. It will start reading at @pos and copy up to @nbytes of
 * data to @ubuf.
 *
 * Returns:
 * This function returns the amount of data that was read (this could be
 * less than @nbytes if the end of the file was reached).
 */
static ssize_t fnic_trace_debugfs_read(struct file *file,
                                        char __user *ubuf,
                                        size_t nbytes,
                                        loff_t *pos)
{
        fnic_dbgfs_t *fnic_dbg_prt = file->private_data;
        int rc = 0;
        rc = simple_read_from_buffer(ubuf, nbytes, pos,
                                  fnic_dbg_prt->buffer,
                                  fnic_dbg_prt->buffer_len);
        return rc;
}

/*
 * fnic_trace_debugfs_release - Release the buffer used to store
 * debugfs file data
 * @inode: The inode pointer
 * @file: The file pointer that contains the buffer to release
 *
 * Description:
 * This routine frees the buffer that was allocated when the debugfs
 * file was opened.
 *
 * Returns:
 * This function returns zero.
 */
static int fnic_trace_debugfs_release(struct inode *inode,
                                          struct file *file)
{
        fnic_dbgfs_t *fnic_dbg_prt = file->private_data;

        vfree(fnic_dbg_prt->buffer);
        kfree(fnic_dbg_prt);
        return 0;
}

static const struct file_operations fnic_trace_ctrl_fops = {
        .owner = THIS_MODULE,
        .open = fnic_trace_ctrl_open,
        .read = fnic_trace_ctrl_read,
        .write = fnic_trace_ctrl_write,
};

static const struct file_operations fnic_trace_debugfs_fops = {
        .owner = THIS_MODULE,
        .open = fnic_trace_debugfs_open,
        .llseek = fnic_trace_debugfs_lseek,
        .read = fnic_trace_debugfs_read,
        .release = fnic_trace_debugfs_release,
};

/*
 * fnic_trace_debugfs_init - Initialize debugfs for fnic trace logging
 *
 * Description:
 * When Debugfs is configured this routine sets up the fnic debugfs
 * file system. If not already created, this routine will create the
 * fnic directory. It will create file trace to log fnic trace buffer
 * output into debugfs and it will also create file trace_enable to
 * control enable/disable of trace logging into trace buffer.
 */
int fnic_trace_debugfs_init(void)
{
        int rc = -1;
        fnic_trace_debugfs_root = debugfs_create_dir("fnic", NULL);
        if (!fnic_trace_debugfs_root) {
                printk(KERN_DEBUG "Cannot create debugfs root\n");
                return rc;
        }
        fnic_trace_enable = debugfs_create_file("tracing_enable",
                                          S_IFREG|S_IRUGO|S_IWUSR,
                                          fnic_trace_debugfs_root,
                                          NULL, &fnic_trace_ctrl_fops);

        if (!fnic_trace_enable) {
                printk(KERN_DEBUG "Cannot create trace_enable file"
                                  " under debugfs");
                return rc;
        }

        fnic_trace_debugfs_file = debugfs_create_file("trace",
                                                  S_IFREG|S_IRUGO|S_IWUSR,
                                                  fnic_trace_debugfs_root,
                                                  NULL,
                                                  &fnic_trace_debugfs_fops);

        if (!fnic_trace_debugfs_file) {
                printk(KERN_DEBUG "Cannot create trace file under debugfs");
                return rc;
        }
        rc = 0;
        return rc;
}

/*
 * fnic_trace_debugfs_terminate - Tear down debugfs infrastructure
 *
 * Description:
 * When Debugfs is configured this routine removes debugfs file system
 * elements that are specific to fnic trace logging.
 */
void fnic_trace_debugfs_terminate(void)
{
        if (fnic_trace_debugfs_file) {
                debugfs_remove(fnic_trace_debugfs_file);
                fnic_trace_debugfs_file = NULL;
        }
        if (fnic_trace_enable) {
                debugfs_remove(fnic_trace_enable);
                fnic_trace_enable = NULL;
        }
        if (fnic_trace_debugfs_root) {
                debugfs_remove(fnic_trace_debugfs_root);
                fnic_trace_debugfs_root = NULL;
        }
}