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SubjectRe: [PATCH v2] PM / wakeup: use seq_open() to show wakeup stats
Hi, Andy

2018-03-14 0:39 GMT+08:00 Andy Shevchenko <andy.shevchenko@gmail.com>:
> On Mon, Mar 5, 2018 at 10:47 AM, Ganesh Mahendran
> <opensource.ganesh@gmail.com> 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

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