Re: [Qemu-devel] [PATCH v5 09/15] hw: Added generic FIFO API.

[Igor Mitsyanko <i.mitsyanko@samsung.com>]

On 08/06/2012 06:16 AM, Peter A. G. Crosthwaite wrote:
> Added a FIFO API that can be used to create and operate byte FIFOs.
>
> Signed-off-by: Peter A. G. Crosthwaite <peter.crosthwaite@petalogix.com>
> ---
>   hw/Makefile.objs |    1 +
>   hw/fifo.c        |   79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   hw/fifo.h        |   47 ++++++++++++++++++++++++++++++++
>   3 files changed, 127 insertions(+), 0 deletions(-)
>   create mode 100644 hw/fifo.c
>   create mode 100644 hw/fifo.h
>
> diff --git a/hw/Makefile.objs b/hw/Makefile.objs
> index 8327e55..6ba570e 100644
> --- a/hw/Makefile.objs
> +++ b/hw/Makefile.objs
> @@ -15,6 +15,7 @@ hw-obj-$(CONFIG_ECC) += ecc.o
>   hw-obj-$(CONFIG_NAND) += nand.o
>   hw-obj-$(CONFIG_PFLASH_CFI01) += pflash_cfi01.o
>   hw-obj-$(CONFIG_PFLASH_CFI02) += pflash_cfi02.o
> +hw-obj-y += fifo.o
Perhaps it'd be better to make it common object and put it into root 
directory, like its done for bitops.c and bitmap.c
>   
>   hw-obj-$(CONFIG_M48T59) += m48t59.o
>   hw-obj-$(CONFIG_ESCC) += escc.o
> diff --git a/hw/fifo.c b/hw/fifo.c
> new file mode 100644
> index 0000000..5e14e1e
> --- /dev/null
> +++ b/hw/fifo.c
> @@ -0,0 +1,79 @@
> +/*
> + * Generic FIFO component, implemented as a circular buffer.
> + *
> + * Copyright (c) 2012 Peter A. G. Crosthwaite
> + *
> + * This program is free software; 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
> + * 2 of the License, or (at your option) any later version.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with this program; if not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include "fifo.h"
> +
> +void fifo8_create(Fifo8 *fifo, uint32_t capacity)
> +{
> +    fifo->data = g_new(uint8_t, capacity);
> +    fifo->capacity = capacity;
> +    fifo->head = 0;
> +    fifo->num = 0;
> +}
> +
> +void fifo8_destroy(Fifo8 *fifo)
> +{
> +    g_free(fifo->data);
> +}
> +
> +void fifo8_push(Fifo8 *fifo, uint8_t data)
> +{
> +    if (fifo->num == fifo->capacity) {
> +        abort();
> +    }
I think its too harsh to abort here (and in pop() too), fifo 
overrun/underrun condition is absolutely normal for most of the devices, 
usually it would just trigger an  interrupt. I suggest return a error 
code instead and let a caller decide what should happen in this situation.
> +    fifo->data[(fifo->head + fifo->num) % fifo->capacity] = data;
> +    fifo->num++;
> +}
> +
> +uint8_t fifo8_pop(Fifo8 *fifo)
> +{
> +    uint8_t ret;
> +
> +    if (fifo->num == 0) {
> +        abort();
> +    }
> +    ret = fifo->data[fifo->head++];
> +    fifo->head %= fifo->capacity;
> +    fifo->num--;
> +    return ret;
> +}
> +
> +void fifo8_reset(Fifo8 *fifo)
> +{
> +    fifo->num = 0;
> +}
> +
> +bool fifo8_is_empty(Fifo8 *fifo)
> +{
> +    return (fifo->num == 0);
> +}
> +
> +bool fifo8_is_full(Fifo8 *fifo)
> +{
> +    return (fifo->num == fifo->capacity);
> +}
> +
> +const VMStateDescription vmstate_fifo8 = {
> +    .name = "SSISlave",
thats not a good name for a generic fifo)
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .minimum_version_id_old = 1,
> +    .fields      = (VMStateField[]) {
too much spaces here
> +        VMSTATE_VBUFFER_UINT32(data, Fifo8, 1, NULL, 0, capacity),
> +        VMSTATE_UINT32(head, Fifo8),
> +        VMSTATE_UINT32(num, Fifo8),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> diff --git a/hw/fifo.h b/hw/fifo.h
> new file mode 100644
> index 0000000..3fb09ff
> --- /dev/null
> +++ b/hw/fifo.h
> @@ -0,0 +1,47 @@
> +#ifndef FIFO_H
> +#define FIFO_H
> +
> +#include "hw.h"
> +
> +typedef struct {
> +    /* All fields are private */
> +    uint8_t *data;
> +    uint32_t capacity;
> +    uint32_t head;
> +    uint32_t num;
> +} Fifo8;
> +
> +/* create a fifo of the specified size */
> +
> +void fifo8_create(Fifo8 *, uint32_t);
> +
> +/* cleanup a fifo */
> +
> +void fifo8_destroy(Fifo8 *);
> +
> +/* push a data byte to the fifo. Behaviour is undefined if the fifo is full */
> +
> +void fifo8_push(Fifo8 *, uint8_t);
> +
> +/* pop a data byte from the fifo. Behviour is undefined if the fifo is empty */
> +
> +uint8_t fifo8_pop(Fifo8 *);
> +
> +/* reset (empty) the fifo */
> +
> +void fifo8_reset(Fifo8 *);
> +
> +bool fifo8_is_empty(Fifo8 *);
> +bool fifo8_is_full(Fifo8 *);
> +
> +extern const VMStateDescription vmstate_fifo8;
> +
> +#define VMSTATE_FIFO8(_field, _state) {                              \
> +    .name       = (stringify(_field)),                               \
> +    .size       = sizeof(Fifo8),                                     \
> +    .vmsd       = &vmstate_fifo8,                                    \
> +    .flags      = VMS_STRUCT,                                        \
> +    .offset     = vmstate_offset_value(_state, _field, Fifo8),       \
> +}
> +
> +#endif /* FIFO_H */