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Posted to commits@nuttx.apache.org by GitBox <gi...@apache.org> on 2020/09/09 01:27:48 UTC
[GitHub] [incubator-nuttx] YuuichiNakamura commented on a change in pull request #1731: note: Rename note driver to noteram driver
YuuichiNakamura commented on a change in pull request #1731:
URL: https://github.com/apache/incubator-nuttx/pull/1731#discussion_r485282212
##########
File path: drivers/note/noteram_driver.c
##########
@@ -0,0 +1,477 @@
+/****************************************************************************
+ * drivers/note/noteram_driver.c
+ *
+ * Copyright (C) 2016 Gregory Nutt. All rights reserved.
+ * Author: Gregory Nutt <gn...@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ * used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <sched.h>
+#include <assert.h>
+#include <errno.h>
+
+#include <nuttx/spinlock.h>
+#include <nuttx/sched_note.h>
+#include <nuttx/note/noteram_driver.h>
+#include <nuttx/fs/fs.h>
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+struct noteram_info_s
+{
+ volatile unsigned int ni_head;
+ volatile unsigned int ni_tail;
+ uint8_t ni_buffer[CONFIG_DRIVER_NOTERAM_BUFSIZE];
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static ssize_t noteram_read(FAR struct file *filep,
+ FAR char *buffer, size_t buflen);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct file_operations g_noteram_fops =
+{
+ NULL, /* open */
+ NULL, /* close */
+ noteram_read, /* read */
+ NULL, /* write */
+ NULL, /* seek */
+ NULL, /* ioctl */
+ NULL /* poll */
+#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
+ , 0 /* unlink */
+#endif
+};
+
+static struct noteram_info_s g_noteram_info;
+
+#ifdef CONFIG_SMP
+static volatile spinlock_t g_noteram_lock;
+#endif
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: noteram_next
+ *
+ * Description:
+ * Return the circular buffer index at offset from the specified index
+ * value, handling wraparound
+ *
+ * Input Parameters:
+ * ndx - Old circular buffer index
+ *
+ * Returned Value:
+ * New circular buffer index
+ *
+ ****************************************************************************/
+
+static inline unsigned int noteram_next(unsigned int ndx,
+ unsigned int offset)
+{
+ ndx += offset;
+ if (ndx >= CONFIG_DRIVER_NOTERAM_BUFSIZE)
+ {
+ ndx -= CONFIG_DRIVER_NOTERAM_BUFSIZE;
+ }
+
+ return ndx;
+}
+
+/****************************************************************************
+ * Name: noteram_length
+ *
+ * Description:
+ * Length of data currently in circular buffer.
+ *
+ * Input Parameters:
+ * None
+ *
+ * Returned Value:
+ * Length of data currently in circular buffer.
+ *
+ ****************************************************************************/
+
+static unsigned int noteram_length(void)
+{
+ unsigned int head = g_noteram_info.ni_head;
+ unsigned int tail = g_noteram_info.ni_tail;
+
+ if (tail > head)
+ {
+ head += CONFIG_DRIVER_NOTERAM_BUFSIZE;
+ }
+
+ return head - tail;
+}
+
+/****************************************************************************
+ * Name: noteram_remove
+ *
+ * Description:
+ * Remove the variable length note from the tail of the circular buffer
+ *
+ * Input Parameters:
+ * None
+ *
+ * Returned Value:
+ * None
+ *
+ * Assumptions:
+ * We are within a critical section.
+ *
+ ****************************************************************************/
+
+static void noteram_remove(void)
+{
+ FAR struct note_common_s *note;
+ unsigned int tail;
+ unsigned int length;
+
+ /* Get the tail index of the circular buffer */
+
+ tail = g_noteram_info.ni_tail;
+ DEBUGASSERT(tail < CONFIG_DRIVER_NOTERAM_BUFSIZE);
+
+ /* Get the length of the note at the tail index */
+
+ note = (FAR struct note_common_s *)&g_noteram_info.ni_buffer[tail];
+ length = note->nc_length;
+ DEBUGASSERT(length <= noteram_length());
+
+ /* Increment the tail index to remove the entire note from the circular
+ * buffer.
+ */
+
+ g_noteram_info.ni_tail = noteram_next(tail, length);
+}
+
+/****************************************************************************
+ * Name: noteram_get
+ *
+ * Description:
+ * Remove the next note from the tail of the circular buffer. The note
+ * is also removed from the circular buffer to make room for further notes.
+ *
+ * Input Parameters:
+ * buffer - Location to return the next note
+ * buflen - The length of the user provided buffer.
+ *
+ * Returned Value:
+ * On success, the positive, non-zero length of the return note is
+ * provided. Zero is returned only if the circular buffer is empty. A
+ * negated errno value is returned in the event of any failure.
+ *
+ ****************************************************************************/
+
+static ssize_t noteram_get(FAR uint8_t *buffer, size_t buflen)
+{
+ FAR struct note_common_s *note;
+ irqstate_t flags;
+ unsigned int remaining;
+ unsigned int tail;
+ ssize_t notelen;
+ size_t circlen;
+
+ DEBUGASSERT(buffer != NULL);
+ flags = enter_critical_section();
+
+ /* Verify that the circular buffer is not empty */
+
+ circlen = noteram_length();
+ if (circlen <= 0)
+ {
+ notelen = 0;
+ goto errout_with_csection;
+ }
+
+ /* Get the index to the tail of the circular buffer */
+
+ tail = g_noteram_info.ni_tail;
+ DEBUGASSERT(tail < CONFIG_DRIVER_NOTERAM_BUFSIZE);
+
+ /* Get the length of the note at the tail index */
+
+ note = (FAR struct note_common_s *)&g_noteram_info.ni_buffer[tail];
+ notelen = note->nc_length;
+ DEBUGASSERT(notelen <= circlen);
+
+ /* Is the user buffer large enough to hold the note? */
+
+ if (buflen < notelen)
+ {
+ /* Remove the large note so that we do not get constipated. */
+
+ noteram_remove();
+
+ /* and return an error */
+
+ notelen = -EFBIG;
+ goto errout_with_csection;
+ }
+
+ /* Loop until the note has been transferred to the user buffer */
+
+ remaining = (unsigned int)notelen;
+ while (remaining > 0)
+ {
+ /* Copy the next byte at the tail index */
+
+ *buffer++ = g_noteram_info.ni_buffer[tail];
+
+ /* Adjust indices and counts */
+
+ tail = noteram_next(tail, 1);
+ remaining--;
+ }
+
+ g_noteram_info.ni_tail = tail;
+
+errout_with_csection:
+ leave_critical_section(flags);
+ return notelen;
+}
+
+/****************************************************************************
+ * Name: noteram_size
+ *
+ * Description:
+ * Return the size of the next note at the tail of the circular buffer.
+ *
+ * Input Parameters:
+ * None.
+ *
+ * Returned Value:
+ * Zero is returned if the circular buffer is empty. Otherwise, the size
+ * of the next note is returned.
+ *
+ ****************************************************************************/
+
+static ssize_t noteram_size(void)
+{
+ FAR struct note_common_s *note;
+ irqstate_t flags;
+ unsigned int tail;
+ ssize_t notelen;
+ size_t circlen;
+
+ flags = enter_critical_section();
+
+ /* Verify that the circular buffer is not empty */
+
+ circlen = noteram_length();
+ if (circlen <= 0)
+ {
+ notelen = 0;
+ goto errout_with_csection;
+ }
+
+ /* Get the index to the tail of the circular buffer */
+
+ tail = g_noteram_info.ni_tail;
+ DEBUGASSERT(tail < CONFIG_DRIVER_NOTERAM_BUFSIZE);
+
+ /* Get the length of the note at the tail index */
+
+ note = (FAR struct note_common_s *)&g_noteram_info.ni_buffer[tail];
+ notelen = note->nc_length;
+ DEBUGASSERT(notelen <= circlen);
+
+errout_with_csection:
+ leave_critical_section(flags);
+ return notelen;
+}
+
+/****************************************************************************
+ * Name: noteram_read
+ ****************************************************************************/
+
+static ssize_t noteram_read(FAR struct file *filep,
+ FAR char *buffer, size_t buflen)
+{
+ ssize_t notelen;
+ ssize_t retlen ;
+
+ DEBUGASSERT(filep != 0 && buffer != NULL && buflen > 0);
+
+ /* Then loop, adding as many notes as possible to the user buffer. */
+
+ retlen = 0;
+ sched_lock();
+ do
+ {
+ /* Get the next note (removing it from the buffer) */
+
+ notelen = noteram_get((FAR uint8_t *)buffer, buflen);
+ if (notelen < 0)
+ {
+ /* We were unable to read the next note, probably because it will
+ * not fit into the user buffer.
+ */
+
+ if (retlen == 0)
+ {
+ /* If nothing was read then report the error. Otherwise,
+ * just silently drop the note.
+ */
+
+ retlen = notelen;
+ }
+
+ break;
+ }
+
+ /* Update pointers from the note that was transferred */
+
+ retlen += notelen;
+ buffer += notelen;
+ buflen -= notelen;
+
+ /* Will the next note fit? There is a race here and even if the next
+ * note will fit, it may fail still when noteram_get() is called.
+ *
+ * It won't fit (or an error occurred). Return what we have without
+ * trying to get the next note (which would cause it to be deleted).
+ */
+
+ notelen = noteram_size();
+ }
+ while (notelen > 0 && notelen <= buflen);
+
+ sched_unlock();
+ return retlen;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: note_add
+ *
+ * Description:
+ * Add the variable length note to the transport layer
+ *
+ * Input Parameters:
+ * note - The note buffer
+ * notelen - The buffer length
+ *
+ * Returned Value:
+ * None
+ *
+ * Assumptions:
+ * We are within a critical section.
+ *
+ ****************************************************************************/
+
+void note_add(FAR const uint8_t *note, uint8_t notelen)
+{
+ unsigned int head;
+ unsigned int next;
+
+#ifdef CONFIG_SMP
+ irqstate_t flags = up_irq_save();
+ spin_lock_wo_note(&g_noteram_lock);
+#endif
+
+ /* Get the index to the head of the circular buffer */
+
+ DEBUGASSERT(note != NULL && notelen < CONFIG_DRIVER_NOTERAM_BUFSIZE);
+ head = g_noteram_info.ni_head;
+
+ /* Loop until all bytes have been transferred to the circular buffer */
+
+ while (notelen > 0)
+ {
+ /* Get the next head index. Would it collide with the current tail
+ * index?
+ */
+
+ next = noteram_next(head, 1);
+ if (next == g_noteram_info.ni_tail)
+ {
+ /* Yes, then remove the note at the tail index */
+
+ noteram_remove();
+ }
+
+ /* Save the next byte at the head index */
+
+ g_noteram_info.ni_buffer[head] = *note++;
+
+ head = next;
+ notelen--;
+ }
+
+ g_noteram_info.ni_head = head;
+
+#ifdef CONFIG_SMP
+ spin_unlock_wo_note(&g_noteram_lock);
+ up_irq_restore(flags);
+#endif
+}
+
+/****************************************************************************
+ * Name: noteram_register
+ *
+ * Description:
+ * Register a serial driver at /dev/note that can be used by an
+ * application to read data from the circular note buffer.
+ *
+ * Input Parameters:
+ * None.
+ *
+ * Returned Value:
+ * Zero is returned if the circular buffer is empty. Otherwise, a negated
+ * errno value is returned.
+ *
+ ****************************************************************************/
+
+int noteram_register(void)
+{
+ return register_driver("dev/note", &g_noteram_fops, 0666, NULL);
Review comment:
The first "/" is missing.
##########
File path: drivers/note/noteram_driver.c
##########
@@ -0,0 +1,477 @@
+/****************************************************************************
+ * drivers/note/noteram_driver.c
+ *
+ * Copyright (C) 2016 Gregory Nutt. All rights reserved.
+ * Author: Gregory Nutt <gn...@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ * used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <sched.h>
+#include <assert.h>
+#include <errno.h>
+
+#include <nuttx/spinlock.h>
+#include <nuttx/sched_note.h>
+#include <nuttx/note/noteram_driver.h>
+#include <nuttx/fs/fs.h>
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+struct noteram_info_s
+{
+ volatile unsigned int ni_head;
+ volatile unsigned int ni_tail;
+ uint8_t ni_buffer[CONFIG_DRIVER_NOTERAM_BUFSIZE];
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static ssize_t noteram_read(FAR struct file *filep,
+ FAR char *buffer, size_t buflen);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct file_operations g_noteram_fops =
+{
+ NULL, /* open */
+ NULL, /* close */
+ noteram_read, /* read */
+ NULL, /* write */
+ NULL, /* seek */
+ NULL, /* ioctl */
+ NULL /* poll */
+#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
+ , 0 /* unlink */
+#endif
+};
+
+static struct noteram_info_s g_noteram_info;
+
+#ifdef CONFIG_SMP
+static volatile spinlock_t g_noteram_lock;
+#endif
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: noteram_next
+ *
+ * Description:
+ * Return the circular buffer index at offset from the specified index
+ * value, handling wraparound
+ *
+ * Input Parameters:
+ * ndx - Old circular buffer index
+ *
+ * Returned Value:
+ * New circular buffer index
+ *
+ ****************************************************************************/
+
+static inline unsigned int noteram_next(unsigned int ndx,
+ unsigned int offset)
+{
+ ndx += offset;
+ if (ndx >= CONFIG_DRIVER_NOTERAM_BUFSIZE)
+ {
+ ndx -= CONFIG_DRIVER_NOTERAM_BUFSIZE;
+ }
+
+ return ndx;
+}
+
+/****************************************************************************
+ * Name: noteram_length
+ *
+ * Description:
+ * Length of data currently in circular buffer.
+ *
+ * Input Parameters:
+ * None
+ *
+ * Returned Value:
+ * Length of data currently in circular buffer.
+ *
+ ****************************************************************************/
+
+static unsigned int noteram_length(void)
+{
+ unsigned int head = g_noteram_info.ni_head;
+ unsigned int tail = g_noteram_info.ni_tail;
+
+ if (tail > head)
+ {
+ head += CONFIG_DRIVER_NOTERAM_BUFSIZE;
+ }
+
+ return head - tail;
+}
+
+/****************************************************************************
+ * Name: noteram_remove
+ *
+ * Description:
+ * Remove the variable length note from the tail of the circular buffer
+ *
+ * Input Parameters:
+ * None
+ *
+ * Returned Value:
+ * None
+ *
+ * Assumptions:
+ * We are within a critical section.
+ *
+ ****************************************************************************/
+
+static void noteram_remove(void)
+{
+ FAR struct note_common_s *note;
+ unsigned int tail;
+ unsigned int length;
+
+ /* Get the tail index of the circular buffer */
+
+ tail = g_noteram_info.ni_tail;
+ DEBUGASSERT(tail < CONFIG_DRIVER_NOTERAM_BUFSIZE);
+
+ /* Get the length of the note at the tail index */
+
+ note = (FAR struct note_common_s *)&g_noteram_info.ni_buffer[tail];
+ length = note->nc_length;
+ DEBUGASSERT(length <= noteram_length());
+
+ /* Increment the tail index to remove the entire note from the circular
+ * buffer.
+ */
+
+ g_noteram_info.ni_tail = noteram_next(tail, length);
+}
+
+/****************************************************************************
+ * Name: noteram_get
+ *
+ * Description:
+ * Remove the next note from the tail of the circular buffer. The note
+ * is also removed from the circular buffer to make room for further notes.
+ *
+ * Input Parameters:
+ * buffer - Location to return the next note
+ * buflen - The length of the user provided buffer.
+ *
+ * Returned Value:
+ * On success, the positive, non-zero length of the return note is
+ * provided. Zero is returned only if the circular buffer is empty. A
+ * negated errno value is returned in the event of any failure.
+ *
+ ****************************************************************************/
+
+static ssize_t noteram_get(FAR uint8_t *buffer, size_t buflen)
+{
+ FAR struct note_common_s *note;
+ irqstate_t flags;
+ unsigned int remaining;
+ unsigned int tail;
+ ssize_t notelen;
+ size_t circlen;
+
+ DEBUGASSERT(buffer != NULL);
+ flags = enter_critical_section();
+
+ /* Verify that the circular buffer is not empty */
+
+ circlen = noteram_length();
+ if (circlen <= 0)
+ {
+ notelen = 0;
+ goto errout_with_csection;
+ }
+
+ /* Get the index to the tail of the circular buffer */
+
+ tail = g_noteram_info.ni_tail;
+ DEBUGASSERT(tail < CONFIG_DRIVER_NOTERAM_BUFSIZE);
+
+ /* Get the length of the note at the tail index */
+
+ note = (FAR struct note_common_s *)&g_noteram_info.ni_buffer[tail];
+ notelen = note->nc_length;
+ DEBUGASSERT(notelen <= circlen);
+
+ /* Is the user buffer large enough to hold the note? */
+
+ if (buflen < notelen)
+ {
+ /* Remove the large note so that we do not get constipated. */
+
+ noteram_remove();
+
+ /* and return an error */
+
+ notelen = -EFBIG;
+ goto errout_with_csection;
+ }
+
+ /* Loop until the note has been transferred to the user buffer */
+
+ remaining = (unsigned int)notelen;
+ while (remaining > 0)
+ {
+ /* Copy the next byte at the tail index */
+
+ *buffer++ = g_noteram_info.ni_buffer[tail];
+
+ /* Adjust indices and counts */
+
+ tail = noteram_next(tail, 1);
+ remaining--;
+ }
+
+ g_noteram_info.ni_tail = tail;
+
+errout_with_csection:
+ leave_critical_section(flags);
+ return notelen;
+}
+
+/****************************************************************************
+ * Name: noteram_size
+ *
+ * Description:
+ * Return the size of the next note at the tail of the circular buffer.
+ *
+ * Input Parameters:
+ * None.
+ *
+ * Returned Value:
+ * Zero is returned if the circular buffer is empty. Otherwise, the size
+ * of the next note is returned.
+ *
+ ****************************************************************************/
+
+static ssize_t noteram_size(void)
+{
+ FAR struct note_common_s *note;
+ irqstate_t flags;
+ unsigned int tail;
+ ssize_t notelen;
+ size_t circlen;
+
+ flags = enter_critical_section();
+
+ /* Verify that the circular buffer is not empty */
+
+ circlen = noteram_length();
+ if (circlen <= 0)
+ {
+ notelen = 0;
+ goto errout_with_csection;
+ }
+
+ /* Get the index to the tail of the circular buffer */
+
+ tail = g_noteram_info.ni_tail;
+ DEBUGASSERT(tail < CONFIG_DRIVER_NOTERAM_BUFSIZE);
+
+ /* Get the length of the note at the tail index */
+
+ note = (FAR struct note_common_s *)&g_noteram_info.ni_buffer[tail];
+ notelen = note->nc_length;
+ DEBUGASSERT(notelen <= circlen);
+
+errout_with_csection:
+ leave_critical_section(flags);
+ return notelen;
+}
+
+/****************************************************************************
+ * Name: noteram_read
+ ****************************************************************************/
+
+static ssize_t noteram_read(FAR struct file *filep,
+ FAR char *buffer, size_t buflen)
+{
+ ssize_t notelen;
+ ssize_t retlen ;
+
+ DEBUGASSERT(filep != 0 && buffer != NULL && buflen > 0);
+
+ /* Then loop, adding as many notes as possible to the user buffer. */
+
+ retlen = 0;
+ sched_lock();
+ do
+ {
+ /* Get the next note (removing it from the buffer) */
+
+ notelen = noteram_get((FAR uint8_t *)buffer, buflen);
+ if (notelen < 0)
+ {
+ /* We were unable to read the next note, probably because it will
+ * not fit into the user buffer.
+ */
+
+ if (retlen == 0)
+ {
+ /* If nothing was read then report the error. Otherwise,
+ * just silently drop the note.
+ */
+
+ retlen = notelen;
+ }
+
+ break;
+ }
+
+ /* Update pointers from the note that was transferred */
+
+ retlen += notelen;
+ buffer += notelen;
+ buflen -= notelen;
+
+ /* Will the next note fit? There is a race here and even if the next
+ * note will fit, it may fail still when noteram_get() is called.
+ *
+ * It won't fit (or an error occurred). Return what we have without
+ * trying to get the next note (which would cause it to be deleted).
+ */
+
+ notelen = noteram_size();
+ }
+ while (notelen > 0 && notelen <= buflen);
+
+ sched_unlock();
+ return retlen;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: note_add
+ *
+ * Description:
+ * Add the variable length note to the transport layer
+ *
+ * Input Parameters:
+ * note - The note buffer
+ * notelen - The buffer length
+ *
+ * Returned Value:
+ * None
+ *
+ * Assumptions:
+ * We are within a critical section.
+ *
+ ****************************************************************************/
+
+void note_add(FAR const uint8_t *note, uint8_t notelen)
+{
+ unsigned int head;
+ unsigned int next;
+
+#ifdef CONFIG_SMP
+ irqstate_t flags = up_irq_save();
+ spin_lock_wo_note(&g_noteram_lock);
+#endif
+
+ /* Get the index to the head of the circular buffer */
+
+ DEBUGASSERT(note != NULL && notelen < CONFIG_DRIVER_NOTERAM_BUFSIZE);
+ head = g_noteram_info.ni_head;
+
+ /* Loop until all bytes have been transferred to the circular buffer */
+
+ while (notelen > 0)
+ {
+ /* Get the next head index. Would it collide with the current tail
+ * index?
+ */
+
+ next = noteram_next(head, 1);
+ if (next == g_noteram_info.ni_tail)
+ {
+ /* Yes, then remove the note at the tail index */
+
+ noteram_remove();
+ }
+
+ /* Save the next byte at the head index */
+
+ g_noteram_info.ni_buffer[head] = *note++;
+
+ head = next;
+ notelen--;
+ }
+
+ g_noteram_info.ni_head = head;
+
+#ifdef CONFIG_SMP
+ spin_unlock_wo_note(&g_noteram_lock);
+ up_irq_restore(flags);
+#endif
+}
+
+/****************************************************************************
+ * Name: noteram_register
+ *
+ * Description:
+ * Register a serial driver at /dev/note that can be used by an
+ * application to read data from the circular note buffer.
+ *
+ * Input Parameters:
+ * None.
+ *
+ * Returned Value:
+ * Zero is returned if the circular buffer is empty. Otherwise, a negated
+ * errno value is returned.
Review comment:
This comment is wrong. Zero is returned if the device is registered successfully.
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