Re: [PATCH v2] PM / wakeup: use seq_open() to show wakeup stats

[Ganesh Mahendran]

Hi, Andy

2018-03-14 0:39 GMT+08:00 Andy Shevchenko <andy.shevchenko@xxxxxxxxx>:
> On Mon, Mar 5, 2018 at 10:47 AM, Ganesh Mahendran
> <opensource.ganesh@xxxxxxxxx> wrote:
>> single_open() interface requires that the whole output must
>> fit into a single buffer. This will lead to timeout when
>> system memory is not in a good situation.
>>
>> This patch use seq_open() to show wakeup stats. This method
>> need only one page, so timeout will not be observed.
>
>> +       if (n == 0) {
>> +               seq_puts(m, "name\t\tactive_count\tevent_count\twakeup_count\t"
>> +                       "expire_count\tactive_since\ttotal_time\tmax_time\t"
>> +                       "last_change\tprevent_suspend_time\n");
>> +       }
>
> Can't you do this once at ->open() stage, for example?

We can not put this at ->open(). Because in seq_open(), the buffer is
not ready,
the seq buffer is allocated in seq_read().

Thanks.

>
>>  static int wakeup_sources_stats_open(struct inode *inode, struct file *file)
>>  {
>> -       return single_open(file, wakeup_sources_stats_show, NULL);
>> +       return seq_open_private(file, &wakeup_sources_stats_seq_ops, sizeof(int));
>>  }
>
> --
> With Best Regards,
> Andy Shevchenko