Messages in this thread | | | Date | Mon, 3 Jun 2019 14:40:29 +0300 | From | Mika Westerberg <> | Subject | Re: [PATCH -next] pwm: pca9685: Remove set but not used variable 'pwm' |
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On Sun, Jun 02, 2019 at 10:18:15AM -0400, Sven Van Asbroeck wrote: > On Sat, Jun 1, 2019 at 12:05 PM Uwe Kleine-König > <u.kleine-koenig@pengutronix.de> wrote: > > > > I didn't look into the driver to try to understand that, but the > > definitely needs a comment to explain for the next person to think they > > can do a cleanup here. > > Certainly.
I agree.
> But if we do restore the old behaviour, there may still be problems. > I'm unsure if the old synchronization was working correctly. > See the example at the end of this email.
I think you are right. pca9685_pwm_request() should take the mutex as long as it is requesting PWM.
> An intuitive way forward would be to use a simple bitfield in > struct pca9685 to track if a specific pwm is in use by either > pwm or gpio. Protected by a mutex.
A flag would probably be easier to understand than the magic we have now. Or then wrap it inside function with an explanation comment:
static inline void pca9685_pwm_set_as_gpio(struct pwm_device *pwm) { /* * We use ->chip_data to convoy the fact that the PWM channel is * being used as GPIO instead of PWM. */ pwm_set_chip_data(pwm, (void *)1) }
static inline void pca9685_pwm_set_as_pwm(struct pwm_device *pwm) { pwm_set_chip_data(pwm, NULL); }
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