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SubjectRe: [PATCH] regmap: add iopoll-like polling macro
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Am Freitag, den 08.07.2016, 16:39 +0200 schrieb Mark Brown:
> On Thu, Jul 07, 2016 at 12:01:43PM +0200, Philipp Zabel wrote:
> > Am Donnerstag, den 07.07.2016, 11:42 +0200 schrieb Mark Brown:
> > > On Wed, Jul 06, 2016 at 04:19:41PM +0200, Philipp Zabel wrote:
>
> > > > This patch adds a macro regmap_read_poll_timeout that works similar
> > > > to the readx_poll_timeout defined in linux/iopoll.h, except that this
> > > > can also return the error value returned by a failed regmap_read.
>
> > > Please make this a proper function.
>
> > I can't, the condition has to be evaluated inside the loop. This is
> > basically a poor man's function template.
>
> Given that the condition is always going to be essentially the same one
> checking that (read & mask) == value we could just parameterize it
> couldn't we?

The iopoll macros also allow comparisons like < > !=, more complicated
expressions, or even function calls.

Granted, the only existing example I am aware of is
drivers/dma/qcom/hidma_ll.c, which calls a static function in
readl_poll_wait_timeout, that evaluates to ((read == 1) || (read == 2)).

There's a similar condition in rt5659_headset_detect, although that may
be dismissed as it's using snd_soc_read and variable delays:
while (i < 5) {
msleep(sleep_time[i]);
val = snd_soc_read(codec, RT5659_EJD_CTRL_2) & 0x0003;
i++;
if (val == 0x1 || val == 0x2 || val == 0x3)
break;
}

A potential user for an inequality condition is
drivers/media/tuners/it913x.c, which has a loop where the condition is
(read != 0):
#define TIMEOUT 50
timeout = jiffies + msecs_to_jiffies(TIMEOUT);
while (!time_after(jiffies, timeout)) {
ret = regmap_read(dev->regmap, 0x80ec82, &utmp);
if (ret)
goto err;

if (utmp)
break;
}

Even if by far the most common cases can be covered as you suggest,
I would find it useful to keep this the same as the other
readx_poll_wait_timeout variants.

regards
Philipp

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