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An interrupt handler can call function sprintf()?

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  An interrupt handler can call function sprintf()? fl <rxjwg98@gmail.com> - 2013-05-19 10:11 -0700
    Re: An interrupt handler can call function sprintf()? Jerry Peters <jerry@example.invalid> - 2013-05-19 20:38 +0000
      Re: An interrupt handler can call function sprintf()? Jerry Peters <jerry@example.invalid> - 2013-05-19 20:58 +0000

#8181 — An interrupt handler can call function sprintf()?

Hi,

I remember it said that C lib function printf() cannot be called in a device driver in Linux. Today I come across the following code snippet. I wonder that sprintf function can be called in the interrupt function?

Interrupt function is part of device driver or not?

Please clarify those concepts if you can. Thanks.






......
irqreturn_t short_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
  struct timeval tv; 
  int written;

  do_gettimeofday(&tv);
/* Write a 16 byte record. Assume PAGE_SIZE is a multiple of 16 */
  written = sprintf((char *)short_head,"%08u.%06u\n",
            (int)(tv.tv_sec % 100000000), (int)(tv.tv_usec));
  BUG_ON(written != 16);
  short_incr_bp(&short_head, written);
  wake_up_interruptible(&short_queue); /* awake any reading process */
  return IRQ_HANDLED;
}

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#8182

fl <rxjwg98@gmail.com> wrote:
> Hi,
> 
> I remember it said that C lib function printf() cannot be called in a device driver in Linux. Today I come across the following code snippet. I wonder that sprintf function can be called in the interrupt function?
> 
It can't, because it writes to a file, stdout. Sprintf "writes" to an
existing string so there's no i/o. Sprintf is just a convenient way to
construct a fancy formatted string.

There is another function, kprintf, which can be used similiarly to
printf, but it wrties to a kernel buffer.

	Jerry

> Interrupt function is part of device driver or not?
> 
> Please clarify those concepts if you can. Thanks.
> 
> 
> 
> 
> 
> 
> ......
> irqreturn_t short_interrupt(int irq, void *dev_id, struct pt_regs *regs)
> {
>  struct timeval tv; 
>  int written;
> 
>  do_gettimeofday(&tv);
> /* Write a 16 byte record. Assume PAGE_SIZE is a multiple of 16 */
>  written = sprintf((char *)short_head,"%08u.%06u\n",
>            (int)(tv.tv_sec % 100000000), (int)(tv.tv_usec));
>  BUG_ON(written != 16);
>  short_incr_bp(&short_head, written);
>  wake_up_interruptible(&short_queue); /* awake any reading process */
>  return IRQ_HANDLED;
> }

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#8183

Jerry Peters <jerry@example.invalid> wrote:
> fl <rxjwg98@gmail.com> wrote:
>> Hi,
>> 
>> I remember it said that C lib function printf() cannot be called in a device driver in Linux. Today I come across the following code snippet. I wonder that sprintf function can be called in the interrupt function?
>> 
> It can't, because it writes to a file, stdout. Sprintf "writes" to an
> existing string so there's no i/o. Sprintf is just a convenient way to
> construct a fancy formatted string.
> 
> There is another function, kprintf, which can be used similiarly to
> printf, but it wrties to a kernel buffer.

Oops, meant printk, not kprintf.

	Jerry

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