Messages in this thread | | | Date | Fri, 20 Feb 2015 16:26:27 -0800 | From | Guenter Roeck <> | Subject | Re: [PATCH v4 7/8] hwmon: pwm-fan: Read PWM FAN configuration from device tree |
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On 02/18/2015 02:07 AM, Lukasz Majewski wrote: > This patch provides code for reading PWM FAN configuration data via > device tree. The pwm-fan can work with full speed when configuration > is not provided. However, errors are propagated when wrong DT bindings > are found. > Additionally the struct pwm_fan_ctx has been extended. > > Signed-off-by: Lukasz Majewski <l.majewski@samsung.com> > --- > Changes for v2: > - Rename pwm_fan_max_states to pwm_fan_cooling_levels > - Moving pwm_fan_of_get_cooling_data() call after setting end enabling PWM FAN > - pwm_fan_of_get_cooling_data() now can fail - preserving old behaviour > - Remove unnecessary dev_err() call > Changes for v3: > - Patch's headline has been reedited > - pwm_fan_of_get_cooling_data() return code is now being checked. > - of_property_count_elems_of_size() is now used instead of_find_property() > - More verbose patch description added > Changes for v4: > - dev_err() has been removed from pwm_fan_of_get_cooling_data() > - Returning -EINVAL when "cooling-levels" are defined in DT, but doesn't > have the value > --- > drivers/hwmon/pwm-fan.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 51 insertions(+), 1 deletion(-) > > diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c > index bd42d39..82cd06a 100644 > --- a/drivers/hwmon/pwm-fan.c > +++ b/drivers/hwmon/pwm-fan.c > @@ -30,7 +30,10 @@ > struct pwm_fan_ctx { > struct mutex lock; > struct pwm_device *pwm; > - unsigned char pwm_value; > + unsigned int pwm_value; > + unsigned int pwm_fan_state; > + unsigned int pwm_fan_max_state; > + unsigned int *pwm_fan_cooling_levels; > }; > > static int __set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm) > @@ -100,6 +103,48 @@ static struct attribute *pwm_fan_attrs[] = { > > ATTRIBUTE_GROUPS(pwm_fan); > > +int pwm_fan_of_get_cooling_data(struct device *dev, struct pwm_fan_ctx *ctx) > +{ > + struct device_node *np = dev->of_node; > + int num, i, ret; > + > + ret = of_property_count_elems_of_size(np, "cooling-levels", > + sizeof(u32)); > + > + if (ret == -EINVAL) > + return 0;
The function returns -EINVAL if there is no such property, but also if prop->length % elem_size != 0. The latter _would_ be an error.
Overall I don't entirely understand why you do not call of_find_property first. If that returns NULL, you would know for sure that the property does not exist, and you would not have to second guess the returned error from of_property_count_elems_of_size.
On a side note, there is of_property_count_u32_elems() to count properties of size u32.
> + > + if (ret <= 0) { > + dev_err(dev, "Wrong data!\n"); > + return ret ? ret : -EINVAL; > + }
If devicetree is not configured, of_property_count_elems_of_size returns -ENOSYS, which is returned, causing the driver to fail loading.
> + > + num = ret; > + ctx->pwm_fan_cooling_levels = devm_kzalloc(dev, num * sizeof(u32), > + GFP_KERNEL); > + if (!ctx->pwm_fan_cooling_levels) > + return -ENOMEM; > + > + ret = of_property_read_u32_array(np, "cooling-levels", > + ctx->pwm_fan_cooling_levels, num); > + if (ret) { > + dev_err(dev, "Property 'cooling-levels' cannot be read!\n"); > + return ret; > + } > + > + for (i = 0; i < num; i++) { > + if (ctx->pwm_fan_cooling_levels[i] > MAX_PWM) { > + dev_err(dev, "PWM fan state[%d]:%d > %d\n", i, > + ctx->pwm_fan_cooling_levels[i], MAX_PWM); > + return -EINVAL; > + } > + } > + > + ctx->pwm_fan_max_state = num - 1; > + > + return 0; > +} > + > static int pwm_fan_probe(struct platform_device *pdev) > { > struct device *hwmon; > @@ -145,6 +190,11 @@ static int pwm_fan_probe(struct platform_device *pdev) > pwm_disable(ctx->pwm); > return PTR_ERR(hwmon); > } > + > + ret = pwm_fan_of_get_cooling_data(&pdev->dev, ctx); > + if (ret) > + return ret; > + > return 0; > } > >
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