[KJ] polling in drivers/cdrom/aztcd.c

[KJ] polling in drivers/cdrom/aztcd.c

[Daniel Marjamäki]

Hello!

I saw this in version 2.6.14.1 of linux.
Does anybody have any input on this matter?

In the file there are several polling routines like the one below, and they are repeatedly called.
The loop will repeat 8 million times before it times out!
I suspect we can make huge improvements here. I'm having 3 improvements in mind:
1. Time out based on actual time rather than on repetitions.
2. Sleep between each repetition. How can I sleep say.. 10-50 us? Is it possible?
3. On time out, return an error code. The callers always assume that the polling succeeded!


static void pa_ok(void)
{
         aztTimeOutCount = 0;
         do {
                 aztIndatum = inb(DATA_PORT);
                 aztTimeOutCount++;
                 if (aztTimeOutCount >= AZT_TIMEOUT) {
                         printk("aztcd: Error Wait PA_OK\n");
                         break;
                 }
         } while (aztIndatum != AFL_PA_OK);
}


Best Regards,
Daniel Marjamäki


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Re: [KJ] polling in drivers/cdrom/aztcd.c

[Alexey Dobriyan]

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On Fri, Nov 18, 2005 at 12:57:18PM +0100, Daniel Marjam?ki wrote:
> I saw this in version 2.6.14.1 of linux.
> Does anybody have any input on this matter?

Bzzrt... The thing was commented out 19 months ago.

#   2004/05/19 16:39:03-07:00 akpm
#   [PATCH] drivers/cdrom/aztcd.c warning fix.
#
#   From: "Luiz Fernando N. Capitulino"
#
#   drivers/cdrom/azctd.c:379: warning: `pa_ok' defined but not used

> static void pa_ok(void)
> {
>         aztTimeOutCount = 0;
>         do {
>                 aztIndatum = inb(DATA_PORT);
>                 aztTimeOutCount++;
>                 if (aztTimeOutCount >= AZT_TIMEOUT) {
>                         printk("aztcd: Error Wait PA_OK\n");
>                         break;
>                 }
>         } while (aztIndatum != AFL_PA_OK);
> }


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