30ad31e9d7
* Make readv/writev implementations update struct uio This can simplify partial result handling. * change the error number on the overflow from EOVERFLOW to EINVAL to match NetBSD * add a commented out uio_offset field. I used "#if 0" here as C comments can't nest. * add a few helper functions Note on uio_copyfrom/uio_copyto: although i'm not quite happy with the "offset" functionality, it's necessary to simplify the adaptation of some drivers like drivers/serial/serial.c, which (ab)uses the user-supplied buffer as a line-buffer.
141 lines
4.3 KiB
C
141 lines
4.3 KiB
C
/****************************************************************************
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* drivers/misc/dev_zero.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <stdbool.h>
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#include <string.h>
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#include <poll.h>
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#include <errno.h>
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#include <nuttx/semaphore.h>
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#include <nuttx/fs/fs.h>
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#include <nuttx/drivers/drivers.h>
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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static ssize_t devzero_readv(FAR struct file *filep, FAR struct uio *uio);
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static ssize_t devzero_writev(FAR struct file *filep, FAR struct uio *uio);
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static int devzero_poll(FAR struct file *filep, FAR struct pollfd *fds,
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bool setup);
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct file_operations g_devzero_fops =
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{
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NULL, /* open */
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NULL, /* close */
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NULL, /* read */
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NULL, /* write */
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NULL, /* seek */
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NULL, /* ioctl */
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NULL, /* mmap */
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NULL, /* truncate */
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devzero_poll, /* poll */
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devzero_readv, /* readv */
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devzero_writev /* writev */
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};
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: devzero_readv
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****************************************************************************/
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static ssize_t devzero_readv(FAR struct file *filep, FAR struct uio *uio)
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{
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size_t total = uio->uio_resid;
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FAR const struct iovec *iov = uio->uio_iov;
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int iovcnt = uio->uio_iovcnt;
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int i;
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UNUSED(filep);
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for (i = 0; i < iovcnt; i++)
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{
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memset(iov[i].iov_base, 0, iov[i].iov_len);
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}
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uio_advance(uio, total);
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return total;
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}
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/****************************************************************************
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* Name: devzero_writev
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****************************************************************************/
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static ssize_t devzero_writev(FAR struct file *filep, FAR struct uio *uio)
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{
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size_t total;
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UNUSED(filep);
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total = uio->uio_resid;
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uio_advance(uio, total);
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return total;
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}
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/****************************************************************************
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* Name: devzero_poll
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****************************************************************************/
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static int devzero_poll(FAR struct file *filep, FAR struct pollfd *fds,
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bool setup)
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{
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UNUSED(filep);
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if (setup)
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{
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poll_notify(&fds, 1, POLLIN | POLLOUT);
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}
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return OK;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: devzero_register
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*
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* Description:
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* Register /dev/zero
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*
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****************************************************************************/
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void devzero_register(void)
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{
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register_driver("/dev/zero", &g_devzero_fops, 0666, NULL);
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}
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