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pwm: Let pwm_set_waveform_might_sleep() fail for exact but impossible requests

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Up to now pwm_set_waveform_might_sleep() returned 1 for exact requests
that couldn't be served exactly. In contrast to
pwm_round_waveform_might_sleep() and pwm_set_waveform_might_sleep() with
exact = false this is an error condition. So simplify handling for
callers of pwm_set_waveform_might_sleep() by returning -EDOM instead of
1 in this case.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/r/20538a46719584dafd8a1395c886780a97dcdf79.1746010245.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
This commit is contained in:
Uwe Kleine-König
2025-04-30 13:55:58 +02:00
committed by Uwe Kleine-König
parent 2006016ec6
commit e866834c8b
1 changed files with 16 additions and 5 deletions
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21
drivers/pwm/core.c
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@@ -404,15 +404,16 @@ static int __pwm_set_waveform(struct pwm_device *pwm,
* Typically a requested waveform cannot be implemented exactly, e.g. because
* you requested .period_length_ns = 100 ns, but the hardware can only set
* periods that are a multiple of 8.5 ns. With that hardware passing @exact =
* true results in pwm_set_waveform_might_sleep() failing and returning 1. If
* @exact = false you get a period of 93.5 ns (i.e. the biggest period not bigger
* than the requested value).
* true results in pwm_set_waveform_might_sleep() failing and returning -EDOM.
* If @exact = false you get a period of 93.5 ns (i.e. the biggest period not
* bigger than the requested value).
* Note that even with @exact = true, some rounding by less than 1 ns is
* possible/needed. In the above example requesting .period_length_ns = 94 and
* @exact = true, you get the hardware configured with period = 93.5 ns.
*
* Returns: 0 on success, 1 if was rounded up (if !@exact) or no perfect match was
* possible (if @exact), or a negative errno
* Returns: 0 on success, 1 if was rounded up (if !@exact), -EDOM if setting
* failed due to the exact waveform not being possible (if @exact), or a
* different negative errno on failure.
* Context: May sleep.
*/
int pwm_set_waveform_might_sleep(struct pwm_device *pwm,
@@ -440,6 +441,16 @@ int pwm_set_waveform_might_sleep(struct pwm_device *pwm,
err = __pwm_set_waveform(pwm, wf, exact);
}
/*
* map err == 1 to -EDOM for exact requests. Also make sure that -EDOM is
* only returned in exactly that case. Note that __pwm_set_waveform()
* should never return -EDOM which justifies the unlikely().
*/
if (unlikely(err == -EDOM))
err = -EINVAL;
else if (exact && err == 1)
err = -EDOM;
return err;
}
EXPORT_SYMBOL_GPL(pwm_set_waveform_might_sleep);