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////////////////////////////////////////////////////////////////////////////////

//

// Filename:    syspipe.h

//

// Project:     CMod S6 System on a Chip, ZipCPU demonstration project

//

// Purpose:     This "device" handles the primary device level interaction of

//              almost all devices on the ZipOS: the pipe.  A pipe, as defined

//      here, is an O/S supported FIFO.  Information written to the FIFO will

//      be read from the FIFO in the order it was received.  Attempts to read

//      from an empty FIFO, or equivalently to write to a full FIFO, will block

//      the reading (writing) process until memory is available.

//

//      In general, each PIPE has three interface functions for reading and

//      another three for writing, together with one for creating an empty pipe.

//      The read functions are:

//

//              kpop_syspipe

//                      Attempts to read one value from the pipe in an interrupt

//                      context.  It is not allowed to fail.  An empty pipe

//                      simply becomes a return value of '1'.

//

//              kread_syspipe

//                      This is where the user trap read() ends up.  When a user

//                      tries to read from a pipe, kread_syspipe checks that the

//                      users request is valid, then transfers control to a

//                      user task level (interrupts enabled) read function.

//

//              uread_syspipe

//                      The user read task.  This task is invoked from the user

//                      trap, calling kread_syspipe at the kernel mode, which

//                      then transitions the read to user mode using

//                      uread_syspipe.

//

//      Writing has it's analogous functions:

//              kpush_syspipe

//                      Attempts to write a value from an interrupt context

//                      to the pipe.  Primarily used when reading from a 

//                      UART driven device.

//              kwrite_syspipe

//              uwrite_syspipie

//

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

////////////////////////////////////////////////////////////////////////////////

//

// Copyright (C) 2015-2016, Gisselquist Technology, LLC

//

// This program is free software (firmware): you can redistribute it and/or

// modify it under the terms of  the GNU General Public License as published

// by the Free Software Foundation, either version 3 of the License, or (at

// your option) any later version.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// You should have received a copy of the GNU General Public License along

// with this program.  (It's in the $(ROOT)/doc directory, run make with no

// target there if the PDF file isn't present.)  If not, see

// <http://www.gnu.org/licenses/> for a copy.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

////////////////////////////////////////////////////////////////////////////////

//

//

#ifndef SYSPIPE_H

#define SYSPIPE_H

extern  void *sys_malloc(int sz);

typedef struct {

        unsigned int    m_mask;

        int             m_head, m_tail;

volatile TASKP          m_rdtask, m_wrtask;

        unsigned int    m_nread, m_nwritten;

        int     dummy;

        int             m_error;

        int             m_buf[1];

} SYSPIPE;

SYSPIPE *new_syspipe(const unsigned int len);

extern  void    kread_syspipe( TASKP tsk, int dev, int *dst, int len);

extern  void    kwrite_syspipe(TASKP tsk, int dev, int *src, int len);

void    kpush_syspipe(SYSPIPE *p, int val);

int     kpop_syspipe(SYSPIPE *p, int *val);

extern  int     num_avail_syspipe(SYSPIPE *p);

extern  int     len_syspipe(SYSPIPE *p);

#define INTERRUPT_READ_TASK     ((TASKP)((unsigned)-1))

// #define      INTERRUPT_WRITE_TASK    ((TASKP)((unsigned)-1))

#endif