Linux write invalid argument

write() returns error:invalid argument when using serial port

I am trying to send data using the serial port but the write command always returns -1.

This is the code for the write command.

and this is the code that calls it

I am getting invalid argument as the error but after looking on google I cant find anything explaning what this means or how to fix it. the closes thing I found was this but it uses st0 not ttyS0 so im not sure if its even the same thing.

can anyone explain what i am doing wrong to get this error and how to fix it ?

3 Answers 3

You should only be examining errno (this includes calling perror() ) if the write call failed, which it indicates by returning -1. If the write succeeds, it leaves errno unchanged.

In order to test for this you should really be assigning the return value to a variable with a signed type — preferably ssize_t — not an unsigned long .

You’re getting EINVAL back from write( ). That means one of your arguments to the function is invalid: EINVAL = *E*rror, *INVAL*id argument. There are three arguments to the function:

write( ) puked when it saw one of those three. So one of those three is wrong.

So put a printf( ) before the call to write( ) and see which one (or two; or three) is wrong.

Where is the actual code (not your memory of the code) that does the open( )? Is the file descriptor returned by open( ) the same one (Comid) you are trying to write( ) onto? If not, there’s your problem.

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cat: write error: Invalid argument

Writing to a custom character device using

cat: write error: Invalid argument

I have changed the permissions to 666 and even tried it with sudo. Still the same results. Also tried echo in similar way

I use Arch linux 4.8.

Edit: The code for the driver

So here we can see that i have even used a device_write function and assigned it in the fops struct to .write. So isn’t it supposed to accept write command and print that statement in the log?

1 Answer 1

In the kernel, each driver provides a series of methods for the various operations that can be performed on a file: open, close, read, write, seek, ioctl, etc. These methods are stored in a struct file_operations . For devices, the methods are provided by the driver that registered that particular device (i.e. that particular combination of block/char, major number and minor number).

A driver may implement only some of the methods; defaults are provided. The defaults generally do nothing and return either success (if it’s sensible to do nothing for that method) or EINVAL (if there is no sensible default and the lack of a method means that the feature is not supported).

“Write error: Invalid argument” means that the write method of the driver returns EINVAL. The most likely explanation is that this driver doesn’t have a write method at all. It is fairly routine for drivers not to support certain actions, e.g. some drivers only support ioctl and not read/write, some drivers are intrinsically unidirectional (e.g. an input device) and only support read and not write or vice versa.

“Invalid argument” has nothing to do with permissions, it’s what the device is able to do. You’d get a permission error if you didn’t have write permission, but you do have permission to talk to the driver. It’s just that what you’re asking the driver to do is something that it has no concept of.

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bash — эхо: ошибка записи: недопустимый аргумент

Я новичок в bash и пытаюсь написать сценарий, который отключает бизнес kworker, как в ответе aMaia здесь.

Пока у меня есть это, которое я запускаю от root:

Но его запуск приводит к:

Что здесь происходит? Я думал, что $i — это просто имя файла, что похоже на правильный синтаксис для эха.

Также приветствуются предложения по очистке / улучшению скрипта в целом!

Обновление: с set -vx , добавленным в начало скрипта, возникает проблемная итерация:

4 ответа

Я думаю, это как-то связано с разрешениями. Я не думаю, что root по умолчанию имеет права на запись в эти файлы. Попробуйте вручную повторить «отключить» для этого файла, даже если вы используете root, вы получите ту же ошибку. Итак, чтобы ваш скрипт заработал, сначала выполните команду chmod 744 для $ i перед эхо, это должно сработать.

У меня тоже была эта проблема в Docker в среде Alpine linux. Я думаю, проблема в том, что echo по умолчанию помещает символ новой строки в конец строки, и ядро ​​не принимает его, но это не так во всех системах. В Docker у меня была эта ошибка, но значение было записано, несмотря на сообщение об ошибке.

Решение (в Bash): echo -n disable >/sys/firmware/acpi/interrupts/gpe66 . Таким образом, новая строка не отображается.

Еще раз проверьте орфографию. echo «disabled» выдаст ошибку записи даже для root, тогда как echo «disable» завершится успешно.

Я получил такое же сообщение об ошибке, пытаясь отключить GPE, который уже был отключен:

После включения я мог отключить его без ошибок:

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Linux tar: /dev/st0: Cannot write: Invalid argument error and solution

Q. When I run tar command it fails with an error that read as follows:

tar: /dev/st0: Cannot write: Invalid argument

How do I fix this error under CentOS / Debian / Fedora / RHEL Linux HP server systems?

A. You need to specify the block factor size. If you try to write a large file on tape this error may occur.

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The data in an archive is grouped into blocks, which are 512 bytes. Blocks are read and written in whole number multiples called records. The number of blocks in a record (i.e., the size of a record in units of 512 bytes) is called the blocking factor.

Archives with blocking factors larger than 20 cannot be read by very old versions of tar, or by some newer versions of tar running on old machines with small address spaces. With GNU tar, the blocking factor of an archive is limited only by the maximum record size of the device containing the archive, or by the amount of available virtual memory.

How do I fix this error?

Set blocking factor to 256 to avoid this error with the -b option. For example, use the following command to backup the /webroot directory and its content to /dev/st0 with 256 blocking factor:
# tar cvf -b 256 /dev/st0 /webroot

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echo: write error: Invalid argument while setting io_poll for NVMe SSD

I am using the following command as a root user to enable Linux kernel polling for a NVMe SSD device.

# echo 1 > /sys/block/nvme2n1/queue/io_poll

I get the following error: bash: echo: write error: Invalid argument

OS details : Ubuntu 16.04, Linux kernel 5.0.0+.

2 Answers 2

Nikhil posted «Error while enabling io_poll for NVMe SSD» to the Linux block mailing list and got a reply from Keith Busch:

Be sure to turn on the polling queues in the nvme driver. There are none by default. The kernel parameter to that [sic] enable them is:

Where ‘X’ is the number of polling queues. I’d recommend at least 1 per CPU socket, but more is better.

From the looks of Nikhil’s reply, it seems io_poll could be set to 1 after the above change had been made.

For context, browsing the kernel source you can the 5.0 kernel introduced the NVMe poll_queues option (this is also alluded to in the storage section of Kernel Newbies 5.0 kernel changelog). Further, a 5.0 commit defaulted poll_queues in to 0 (at the time of writing in late 2019 we’re currently up to 5.5-rc2 and this is still the case).

Further, it looks like Frank Ober (who posted an answer to this question as @FrankO) asked «why the change was made» in the «Polled io for Linux kernel 5.x» Linux block mailing list thread and also received a reply from Keith:

The original polling implementation shared resources that generate interrupts. This prevents it from running as fast as it can, so dedicated polling queues are used now.

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