[alsa-devel] [PATCH 05/11] drivers: char: axd: add buffers manipulation files
Qais Yousef
qais.yousef at imgtec.com
Tue Oct 28 12:26:23 CET 2014
these files support initilising and managing access to the shared
buffers area in memory that is used to exchange data between AXD
and linux
Signed-off-by: Qais Yousef <qais.yousef at imgtec.com>
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: <alsa-devel at alsa-project.org>
---
drivers/char/axd/axd_buffers.c | 245 +++++++++++++++++++++++++++++++++++++++++
drivers/char/axd/axd_buffers.h | 70 ++++++++++++
2 files changed, 315 insertions(+)
create mode 100644 drivers/char/axd/axd_buffers.c
create mode 100644 drivers/char/axd/axd_buffers.h
diff --git a/drivers/char/axd/axd_buffers.c b/drivers/char/axd/axd_buffers.c
new file mode 100644
index 000000000000..fefa7f85f4db
--- /dev/null
+++ b/drivers/char/axd/axd_buffers.c
@@ -0,0 +1,245 @@
+/*
+ * Copyright (C) 2011-2014 Imagination Technologies Ltd.
+ *
+ * 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.
+ *
+ * AXD generic buffer management API.
+ */
+#include <linux/err.h>
+#include <linux/slab.h>
+
+#include "axd_buffers.h"
+
+#ifdef DEBUG_BUFFERS
+#define debugbuf printk
+#else
+#define debugbuf(format, ...)
+#endif
+
+/**
+ * axd_buffer_init - sets up axd buffer as a pool of fixed sized buffers.
+ * @address: starting address of the buffer as set up in the system
+ * @total_size: total size of available buffer
+ * @element_size: size of each buffer element
+ *
+ * axd_buffer_t *buffer is a memory pool of size @element_size and starting at
+ * address @address and of @total_size size.
+ */
+static int bufferq_init(struct axd_bufferq *bufferq, const char *name,
+ char *address, unsigned int num_elements,
+ unsigned int element_size, unsigned int nonblock)
+{
+ int i;
+ char **queue;
+ unsigned int *size;
+
+ strncpy(bufferq->name, name, 16);
+ bufferq->stride = element_size;
+ bufferq->max = num_elements;
+ bufferq->rd_idx = 0;
+ bufferq->wr_idx = 0;
+ bufferq->nonblock = nonblock;
+ queue = kcalloc(num_elements, sizeof(char *), GFP_KERNEL);
+ if (!queue)
+ return -ENOMEM;
+ bufferq->queue = queue;
+ size = kcalloc(num_elements, sizeof(unsigned int), GFP_KERNEL);
+ if (!size) {
+ kfree(queue);
+ bufferq->queue = NULL;
+ return -ENOMEM;
+ }
+ bufferq->size = size;
+ /*
+ * setup the queue with all available buffer addresses if the base
+ * address is passed. Set it up as emptry if base address is NULL.
+ */
+ if (address) {
+ for (i = 0; i < num_elements; i++) {
+ queue[i] = address + (element_size * i);
+ size[i] = element_size;
+ }
+ sema_init(&bufferq->rd_sem, num_elements);
+ sema_init(&bufferq->wr_sem, 0);
+ } else {
+ for (i = 0; i < num_elements; i++) {
+ queue[i] = NULL;
+ size[i] = element_size;
+ }
+ sema_init(&bufferq->rd_sem, 0);
+ sema_init(&bufferq->wr_sem, num_elements);
+ }
+ spin_lock_init(&bufferq->q_rdlock);
+ spin_lock_init(&bufferq->q_wrlock);
+ debugbuf("Initialized %s of %d elements of size %d bytes\n",
+ name, num_elements, element_size);
+ debugbuf("Address of %s: 0x%08X\n", name, (unsigned int)bufferq);
+ return 0;
+}
+
+int axd_bufferq_init(struct axd_bufferq *bufferq, const char *name,
+ char *address, unsigned int num_elements,
+ unsigned int element_size, unsigned int nonblock)
+{
+ return bufferq_init(bufferq,
+ name, address, num_elements, element_size, nonblock);
+}
+
+int axd_bufferq_init_empty(struct axd_bufferq *bufferq, const char *name,
+ unsigned int num_elements, unsigned int element_size,
+ unsigned int nonblock)
+{
+ return bufferq_init(bufferq,
+ name, NULL, num_elements, element_size, nonblock);
+}
+
+void axd_bufferq_clear(struct axd_bufferq *bufferq)
+{
+ kfree(bufferq->queue);
+ kfree(bufferq->size);
+ bufferq->queue = NULL;
+ bufferq->size = NULL;
+}
+
+/**
+ * axd_buffer_take - returns a valid buffer pointer
+ * @buffer: the buffers pool to be accessed
+ *
+ * This function will go into interruptible sleep if the pool is empty.
+ */
+char *axd_bufferq_take(struct axd_bufferq *bufferq, int *buf_size)
+{
+ char *buf;
+ int ret;
+
+ if (!bufferq->queue)
+ return NULL;
+
+ debugbuf("--(%s)-- taking new buffer\n", bufferq->name);
+ if (bufferq->nonblock) {
+ ret = down_trylock(&bufferq->rd_sem);
+ if (ret)
+ return ERR_PTR(-EAGAIN);
+
+ } else {
+ ret = down_interruptible(&bufferq->rd_sem);
+ if (ret)
+ return ERR_PTR(-ERESTARTSYS);
+ if (bufferq->abort_take) {
+ bufferq->abort_take = 0;
+ return ERR_PTR(-ERESTARTSYS);
+ }
+ }
+ /*
+ * must ensure we have one access at a time to the queue and rd_idx
+ * to be preemption and SMP safe
+ * Sempahores will ensure that we will only read after a complete write
+ * has finished, so we will never read and write from the same location.
+ */
+ spin_lock(&bufferq->q_rdlock);
+ buf = bufferq->queue[bufferq->rd_idx];
+ if (buf_size)
+ *buf_size = bufferq->size[bufferq->rd_idx];
+ bufferq->rd_idx++;
+ if (bufferq->rd_idx >= bufferq->max)
+ bufferq->rd_idx = 0;
+ spin_unlock(&bufferq->q_rdlock);
+ up(&bufferq->wr_sem);
+ debugbuf("--(%s)-- took buffer <0x%08X>\n", bufferq->name,
+ (unsigned int)buf);
+ return buf;
+}
+
+/**
+ * axd_buffer_put - returns a buffer to the pool.
+ * @buffer: the buffers pool to be accessed
+ * @buf: the buffer to be returned.
+ *
+ * This function will go into interruptible sleep if the pool is full.
+ */
+int axd_bufferq_put(struct axd_bufferq *bufferq, char *buf, int buf_size)
+{
+ int ret;
+
+ if (!bufferq->queue)
+ return 0;
+
+ if (buf_size < 0)
+ buf_size = bufferq->stride;
+
+ debugbuf("++(%s)++ returning buffer\n", bufferq->name);
+ if (bufferq->nonblock) {
+ ret = down_trylock(&bufferq->wr_sem);
+ if (ret)
+ return -EAGAIN;
+
+ } else {
+ ret = down_interruptible(&bufferq->wr_sem);
+ if (ret)
+ return -ERESTARTSYS;
+ if (bufferq->abort_put) {
+ bufferq->abort_put = 0;
+ return -ERESTARTSYS;
+ }
+ }
+ /*
+ * must ensure we have one access at a time to the queue and wr_idx
+ * to be preemption and SMP safe.
+ * Semaphores will ensure that we only write after a complete read has
+ * finished, so we will never write and read from the same location.
+ */
+ spin_lock(&bufferq->q_wrlock);
+ bufferq->queue[bufferq->wr_idx] = buf;
+ bufferq->size[bufferq->wr_idx] = buf_size;
+ bufferq->wr_idx++;
+ if (bufferq->wr_idx >= bufferq->max)
+ bufferq->wr_idx = 0;
+ spin_unlock(&bufferq->q_wrlock);
+ up(&bufferq->rd_sem);
+ debugbuf("++(%s)++ returned buffer <0x%08X>\n", bufferq->name,
+ (unsigned int)buf);
+ return 0;
+}
+
+int axd_bufferq_is_full(struct axd_bufferq *bufferq)
+{
+ int ret;
+ /*
+ * if we can't put a buffer, then we're full.
+ */
+ ret = down_trylock(&bufferq->wr_sem);
+ if (!ret)
+ up(&bufferq->wr_sem);
+ return ret;
+}
+
+int axd_bufferq_is_empty(struct axd_bufferq *bufferq)
+{
+ int ret;
+ /*
+ * if we can't take more buffers, then its empty.
+ */
+ ret = down_trylock(&bufferq->rd_sem);
+ if (!ret)
+ up(&bufferq->rd_sem);
+ return ret;
+}
+
+void axd_bufferq_abort_take(struct axd_bufferq *bufferq)
+{
+ if (axd_bufferq_is_empty(bufferq)) {
+ bufferq->abort_take = 1;
+ up(&bufferq->rd_sem);
+ }
+}
+
+void axd_bufferq_abort_put(struct axd_bufferq *bufferq)
+{
+ if (axd_bufferq_is_full(bufferq)) {
+ bufferq->abort_put = 1;
+ up(&bufferq->wr_sem);
+ }
+}
diff --git a/drivers/char/axd/axd_buffers.h b/drivers/char/axd/axd_buffers.h
new file mode 100644
index 000000000000..745a5e28b36f
--- /dev/null
+++ b/drivers/char/axd/axd_buffers.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2011-2014 Imagination Technologies Ltd.
+ *
+ * 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.
+ *
+ * AXD generic buffer management API.
+ */
+#ifndef AXD_BUFFERS_H_
+#define AXD_BUFFERS_H_
+
+#include <linux/semaphore.h>
+#include <linux/spinlock.h>
+
+/**
+ * struct axd_bufferq - axd buffer management structure
+ * @name: name of the buffer queue
+ * @stride: the space between buffers in memory
+ * @max: total number of buffers this queue can handle
+ * @rd_idx: read index of the circular buffer
+ * @wr_idx: write index of the circular buffer
+ * @rd_sem: semaphore to block when full
+ * @wr_sem: semaphore to block when empty
+ * @q_rdlock: smp critical section protection for reads
+ * @q_wrlock: smp critical section protection for writes
+ * @queue: array of pointers to buffer addresses
+ * @size: array of buffer's actual amount of data it has inside or it can
+ * store.
+ * @nonblock: return an error instead of block when empty/full
+ * @abort_take: abort any pending blocked take operation
+ * @abort_put: abort any pending blocked put operation
+ *
+ * axd_bufferq takes a contiguous memory region and divides it into smaller
+ * buffers regions of equal size and represents it as a queue. To avoid
+ * excessive locking it's done as a circular buffer queue.
+ */
+struct axd_bufferq {
+ char name[16];
+ unsigned int stride;
+ unsigned int max;
+ unsigned int rd_idx;
+ unsigned int wr_idx;
+ struct semaphore rd_sem;
+ struct semaphore wr_sem;
+ spinlock_t q_rdlock;
+ spinlock_t q_wrlock;
+ char **queue;
+ unsigned int *size;
+ unsigned int nonblock;
+ unsigned int abort_take;
+ unsigned int abort_put;
+};
+
+int axd_bufferq_init(struct axd_bufferq *bufferq, const char *name,
+ char *address, unsigned int num_elements,
+ unsigned int element_size, unsigned int nonblock);
+int axd_bufferq_init_empty(struct axd_bufferq *bufferq, const char *name,
+ unsigned int num_elements, unsigned int element_size,
+ unsigned int nonblock);
+void axd_bufferq_clear(struct axd_bufferq *bufferq);
+char *axd_bufferq_take(struct axd_bufferq *bufferq, int *buf_size);
+int axd_bufferq_put(struct axd_bufferq *bufferq, char *buf, int buf_size);
+int axd_bufferq_is_full(struct axd_bufferq *bufferq);
+int axd_bufferq_is_empty(struct axd_bufferq *bufferq);
+void axd_bufferq_abort_take(struct axd_bufferq *bufferq);
+void axd_bufferq_abort_put(struct axd_bufferq *bufferq);
+
+#endif /* AXD_BUFFERS_H_ */
--
2.1.0
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