linux-kernel - Re: [PATCH] samples: Fix `echo 1 > /proc/int-fifo` never return error

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Date:	Wed, 4 Feb 2015 18:35:35 +0800
From:	"long.wanglong" <long.wanglong@...wei.com>
To:	Stefani Seibold <stefani@...bold.net>
CC:	<peifeiyue@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] samples: Fix `echo 1 > /proc/int-fifo` never return error

On 2015/2/4 18:18, Stefani Seibold wrote:
> The example is intended for int types, not for strings. So it is not a
> bug, it's a feature ;-) But anyway, if you prefer to handle with strings
> your are okay by me.
> 
hi,Stefani Seibold

Thanks you for your reply. another question?

This example export the interface '/proc/int-fifo', and how to use it?
Write and read it through system call, or the command `cat` and `echo`?

Best Regards
Wang Long

> Am Dienstag, den 03.02.2015, 11:51 +0000 schrieb Wang Long:
>> echo 99 > /proc/int-fifo       ------------> Never return
>> echo 1000 > /proc/int-fifo     ------------> Never return
>>
>> this patch fix it.
>>
>> Signed-off-by: Wang Long <long.wanglong@...wei.com>
>> ---
>>  samples/kfifo/inttype-example.c | 51 ++++++++++++++++++++++++++++++++---------
>>  1 file changed, 40 insertions(+), 11 deletions(-)
>>
>> diff --git a/samples/kfifo/inttype-example.c b/samples/kfifo/inttype-example.c
>> index 8dc3c2e..cc0db5f 100644
>> --- a/samples/kfifo/inttype-example.c
>> +++ b/samples/kfifo/inttype-example.c
>> @@ -6,6 +6,7 @@
>>   * Released under the GPL version 2 only.
>>   *
>>   */
>> +#include <asm/uaccess.h>
>>  
>>  #include <linux/init.h>
>>  #include <linux/module.h>
>> @@ -23,6 +24,9 @@
>>  /* name of the proc entry */
>>  #define	PROC_FIFO	"int-fifo"
>>  
>> +/* Worst case buffer size needed for holding an integer. */
>> +#define PROC_NUMBUF 13
>> +
>>  /* lock for procfs read access */
>>  static DEFINE_MUTEX(read_lock);
>>  
>> @@ -108,33 +112,58 @@ static int __init testfunc(void)
>>  static ssize_t fifo_write(struct file *file, const char __user *buf,
>>  						size_t count, loff_t *ppos)
>>  {
>> -	int ret;
>> -	unsigned int copied;
>> +	char buffer[PROC_NUMBUF];
>> +	int value;
>> +	int err;
>>  
>> -	if (mutex_lock_interruptible(&write_lock))
>> -		return -ERESTARTSYS;
>> +	memset(buffer, 0, sizeof(buffer));
>>  
>> -	ret = kfifo_from_user(&test, buf, count, &copied);
>> +	if (count > sizeof(buffer) - 1)
>> +		count = sizeof(buffer) - 1;
>> +	if (copy_from_user(buffer, buf, count)) {
>> +		err = -EFAULT;
>> +		goto out;
>> +	}
>>  
>> -	mutex_unlock(&write_lock);
>> +	err = kstrtoint(strstrip(buffer), 0, &value);
>> +	if (err)
>> +		goto out;
>> +
>> +	if (kfifo_is_full(&test)) {
>> +		err = -EINVAL;
>> +		goto out;
>> +	}
>>  
>> -	return ret ? ret : copied;
>> +	if (mutex_lock_interruptible(&write_lock))
>> +		return -ERESTARTSYS;
>> +	kfifo_put(&test, value);
>> +	mutex_unlock(&write_lock);
>> +out:
>> +	return err < 0 ? err : count;
>>  }
>>  
>>  static ssize_t fifo_read(struct file *file, char __user *buf,
>>  						size_t count, loff_t *ppos)
>>  {
>> -	int ret;
>> -	unsigned int copied;
>> +	char buffer[PROC_NUMBUF * FIFO_SIZE];
>> +	int value;
>> +	size_t	len = 0;
>> +	ssize_t	ret = -1;
>> +
>> +	memset(buffer, 0, sizeof(buffer));
>>  
>>  	if (mutex_lock_interruptible(&read_lock))
>>  		return -ERESTARTSYS;
>>  
>> -	ret = kfifo_to_user(&test, buf, count, &copied);
>> +	while (!kfifo_is_empty(&test)){
>> +		ret = kfifo_get(&test, &value);
>> +		len = snprintf(buffer, sizeof(buffer), "%s%d\n", buffer, value);
>> +	}
>>  
>>  	mutex_unlock(&read_lock);
>> +	ret = copy_to_user(buf, buffer, len);
>>  
>> -	return ret ? ret : copied;
>> +	return ret ? ret : len;
>>  }
>>  
>>  static const struct file_operations fifo_fops = {
> 
> 
> 
> .
> 


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