The standard devices are currently broken since they have the size ~0. As now files use loff_t as file size which is a signed type the read implementation gets confused and now returns -1. The current implementation also has the (somewhat theorical) problem that we do not have real streaming devices, so /dev/zero went out of zeroes after reading 4GB (or now LLONG_MAX). This patch introduces a new cdev flag DEVFS_IS_CHARACTER_DEV and a new file size flag FILE_SIZE_STREAM which makes it possible to create real stream devices instead. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
107 lines
2.2 KiB
C
107 lines
2.2 KiB
C
/*
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* Copyright (c) 2011 Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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* MA 02111-1307 USA
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*/
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#include <common.h>
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#include <init.h>
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static ssize_t zero_read(struct cdev *cdev, void *buf, size_t count, loff_t offset, ulong flags)
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{
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memset(buf, 0, count);
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return count;
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}
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static struct file_operations zeroops = {
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.read = zero_read,
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.lseek = dev_lseek_default,
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};
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static int zero_init(void)
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{
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struct cdev *cdev;
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cdev = xzalloc(sizeof (*cdev));
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cdev->name = "zero";
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cdev->flags = DEVFS_IS_CHARACTER_DEV;
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cdev->ops = &zeroops;
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devfs_create(cdev);
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return 0;
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}
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device_initcall(zero_init);
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static ssize_t full_read(struct cdev *cdev, void *buf, size_t count, loff_t offset, ulong flags)
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{
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memset(buf, 0xff, count);
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return count;
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}
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static struct file_operations fullops = {
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.read = full_read,
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.lseek = dev_lseek_default,
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};
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static int full_init(void)
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{
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struct cdev *cdev;
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cdev = xzalloc(sizeof (*cdev));
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cdev->name = "full";
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cdev->flags = DEVFS_IS_CHARACTER_DEV;
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cdev->ops = &fullops;
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devfs_create(cdev);
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return 0;
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}
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device_initcall(full_init);
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static ssize_t null_write(struct cdev *cdev, const void *buf, size_t count, loff_t offset, ulong flags)
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{
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return count;
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}
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static struct file_operations nullops = {
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.write = null_write,
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.lseek = dev_lseek_default,
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};
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static int null_init(void)
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{
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struct cdev *cdev;
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cdev = xzalloc(sizeof (*cdev));
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cdev->name = "null";
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cdev->flags = DEVFS_IS_CHARACTER_DEV;
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cdev->ops = &nullops;
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devfs_create(cdev);
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return 0;
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}
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device_initcall(null_init);
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