761ee81956
currently, nuttx implements readv/writev on the top of read/write. while it might work for the simplest cases, it's broken by design. for example, it's impossible to make it work correctly for files which need to preserve data boundaries without allocating a single contiguous buffer. (udp socket, some character devices, etc) this change is a start of the migration to a better design. that is, implement read/write on the top of readv/writev. to avoid a single huge change, following things will NOT be done in this commit: * fix actual bugs caused by the original readv-based-on-read design. (cf. https://github.com/apache/nuttx/pull/12674) * adapt filesystems/drivers to actually benefit from the new interface. (except a few trivial examples) * eventually retire the old interface. * retire read/write syscalls. implement them in libc instead. * pread/pwrite/preadv/pwritev (except the introduction of struct uio, which is a preparation to back these variations with the new interface.)
172 lines
5.2 KiB
C
172 lines
5.2 KiB
C
/****************************************************************************
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* drivers/loop/loop.c
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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 <errno.h>
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#include <nuttx/fs/fs.h>
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#include <nuttx/fs/loop.h>
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#ifdef CONFIG_DEV_LOOP
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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static ssize_t loop_readv(FAR struct file *filep,
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FAR const struct uio *uio);
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static ssize_t loop_writev(FAR struct file *filep,
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FAR const struct uio *uio);
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static int loop_ioctl(FAR struct file *filep, int cmd,
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unsigned long arg);
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct file_operations g_loop_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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loop_ioctl, /* ioctl */
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NULL, /* mmap */
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NULL, /* truncate */
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NULL, /* poll */
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loop_readv, /* readv */
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loop_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: loop_read
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****************************************************************************/
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static ssize_t loop_readv(FAR struct file *filep,
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FAR const struct uio *uio)
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{
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return 0; /* Return EOF */
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}
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/****************************************************************************
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* Name: loop_write
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****************************************************************************/
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static ssize_t loop_writev(FAR struct file *filep,
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FAR const struct uio *uio)
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{
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return uio_total_len(uio); /* Say that everything was written */
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}
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/****************************************************************************
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* Name: loop_ioctl
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****************************************************************************/
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static int loop_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
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{
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int ret;
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switch (cmd)
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{
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/* Command: LOOPIOC_SETUP
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* Description: Setup the loop device
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* Argument: A pointer to a read-only instance of struct losetup_s.
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* Dependencies: The loop device must be enabled (CONFIG_DEV_LOOP=y)
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*/
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case LOOPIOC_SETUP:
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{
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FAR struct losetup_s *setup =
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(FAR struct losetup_s *)((uintptr_t)arg);
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if (setup == NULL)
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{
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ret = -EINVAL;
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}
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else
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{
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ret = losetup(setup->devname, setup->filename, setup->sectsize,
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setup->offset, setup->readonly);
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}
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}
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break;
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/* Command: LOOPIOC_TEARDOWN
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* Description: Teardown a loop device previously setup via
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LOOPIOC_SETUP
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* Argument: A read-able pointer to the path of the device to be
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* torn down
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* Dependencies: The loop device must be enabled (CONFIG_DEV_LOOP=y)
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*/
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case LOOPIOC_TEARDOWN:
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{
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FAR const char *devname = (FAR const char *)((uintptr_t)arg);
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if (devname == NULL)
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{
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ret = -EINVAL;
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}
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else
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{
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ret = loteardown(devname);
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}
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}
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break;
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default:
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ret = -ENOTTY;
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break;
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}
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return ret;
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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: loop_register
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*
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* Description:
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* Register /dev/null
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*
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****************************************************************************/
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void loop_register(void)
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{
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register_driver("/dev/loop", &g_loop_fops, 0666, NULL);
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}
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#endif /* CONFIG_DEV_LOOP */
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