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([2600:8803:e7e4:1d00:4d99:814b:57f9:f83b]) by smtp.gmail.com with ESMTPSA id 5614622812f47-43f51258ce4sm549871b6e.30.2025.09.25.14.10.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 25 Sep 2025 14:10:15 -0700 (PDT) Message-ID: <2a503edb-fe9f-4d61-92c0-c1083a028e19@baylibre.com> Date: Thu, 25 Sep 2025 16:10:14 -0500 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/5] iio: add processed write API To: Romain Gantois , Liam Girdwood , Mark Brown , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Jonathan Cameron , =?UTF-8?Q?Nuno_S=C3=A1?= , Andy Shevchenko Cc: Hans de Goede , Thomas Petazzoni , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-iio@vger.kernel.org References: <20250925-ltm8054-driver-v2-0-bb61a401a0dc@bootlin.com> <20250925-ltm8054-driver-v2-2-bb61a401a0dc@bootlin.com> Content-Language: en-US From: David Lechner In-Reply-To: <20250925-ltm8054-driver-v2-2-bb61a401a0dc@bootlin.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/25/25 7:37 AM, Romain Gantois wrote: > Add a function to allow IIO consumers to write a processed value to a > channel. > > Signed-off-by: Romain Gantois > --- > drivers/iio/inkern.c | 120 +++++++++++++++++++++++++++++++++++++++++++ > include/linux/iio/consumer.h | 36 +++++++++++++ > 2 files changed, 156 insertions(+) > > diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c > index 2a1ecef2b82007f5ee8e8d0f8b35846bc4d2f94a..a6ec724b7c1fb197e6261c1162f8315deda20fd7 100644 > --- a/drivers/iio/inkern.c > +++ b/drivers/iio/inkern.c > @@ -631,6 +631,57 @@ int iio_multiply_value(int *result, s64 multiplier, > } > EXPORT_SYMBOL_GPL(iio_multiply_value); > > +int iio_divide_by_value(int *result, s64 numerator, > + unsigned int type, int val, int val2) > +{ > + s64 tmp_num, tmp_den; > + > + switch (type) { > + case IIO_VAL_INT: > + tmp_num = numerator; > + tmp_den = val; > + break; > + case IIO_VAL_INT_PLUS_MICRO: > + case IIO_VAL_INT_PLUS_NANO: > + switch (type) { > + case IIO_VAL_INT_PLUS_MICRO: > + tmp_num = MICRO; > + tmp_den = MICRO; > + break; > + > + case IIO_VAL_INT_PLUS_NANO: > + tmp_num = NANO; > + tmp_den = NANO; > + break; > + } > + > + tmp_num *= (s64)numerator; > + tmp_den = (s64)abs(val) * tmp_den + (s64)abs(val2); > + > + if (val < 0 || val2 < 0) > + tmp_num *= -1; > + > + break; > + case IIO_VAL_FRACTIONAL: > + tmp_num = (s64)numerator * (s64)val2; > + tmp_den = val; > + break; > + case IIO_VAL_FRACTIONAL_LOG2: > + tmp_num = (s64)numerator << val2; > + tmp_den = val; > + break; > + default: > + return -EINVAL; > + } > + > + if (!tmp_den) > + return -ERANGE; > + > + *result = div64_s64(tmp_num, tmp_den); > + > + return IIO_VAL_INT; > +} > + > static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan, > int raw, int *processed, > unsigned int scale) > @@ -699,6 +750,53 @@ int iio_convert_raw_to_processed(struct iio_channel *chan, int raw, > } > EXPORT_SYMBOL_GPL(iio_convert_raw_to_processed); > > +static int iio_convert_processed_to_raw_unlocked(struct iio_channel *chan, > + int processed, int *raw, > + unsigned int scale) > +{ > + int scale_type, scale_val, scale_val2; > + int offset_type, offset_val, offset_val2; > + int ret; > + > + scale_type = iio_channel_read(chan, &scale_val, &scale_val2, > + IIO_CHAN_INFO_SCALE); > + if (scale_type >= 0) { > + ret = iio_divide_by_value(raw, processed, scale_type, scale_val, scale_val2); > + if (ret < 0) > + return ret; > + } else { > + *raw = processed; > + } > + > + if (!scale) > + return -ERANGE; > + > + *raw = div_s64(*raw, scale); > + > + offset_type = iio_channel_read(chan, &offset_val, &offset_val2, > + IIO_CHAN_INFO_OFFSET); > + if (offset_type >= 0) { > + switch (offset_type) { > + case IIO_VAL_INT: > + case IIO_VAL_INT_PLUS_MICRO: > + case IIO_VAL_INT_PLUS_NANO: > + break; > + case IIO_VAL_FRACTIONAL: > + offset_val /= offset_val2; > + break; > + case IIO_VAL_FRACTIONAL_LOG2: > + offset_val >>= offset_val2; > + break; > + default: > + return -EINVAL; > + } > + > + *raw -= offset_val; > + } There are some rounding biases in this function, but I'm not sure if it is worth trying to make a perfectly fair function. > + > + return 0; > +} > + > int iio_read_channel_attribute(struct iio_channel *chan, int *val, int *val2, > enum iio_chan_info_enum attribute) > { > @@ -1035,3 +1133,25 @@ ssize_t iio_read_channel_label(struct iio_channel *chan, char *buf) > return do_iio_read_channel_label(chan->indio_dev, chan->channel, buf); > } > EXPORT_SYMBOL_GPL(iio_read_channel_label); > + > +int iio_write_channel_processed_scale(struct iio_channel *chan, int val, > + unsigned int scale) > +{ > + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(chan->indio_dev); > + int ret, processed; > + > + scoped_guard(mutex, &iio_dev_opaque->info_exist_lock) { Can just use regular guard(mutex)() here and save some indent. > + if (!chan->indio_dev->info) > + return -ENODEV; > + > + ret = iio_convert_processed_to_raw_unlocked(chan, val, &processed, scale); > + if (ret) > + return ret; > + > + ret = iio_channel_write(chan, processed, 0, IIO_CHAN_INFO_RAW); And this can return directly. > + } > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(iio_write_channel_processed_scale); > + > diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h > index c8c6261c81f934480e16854412e269207be60adc..dc84b8b4c61911d1a58427f1a9c798cae3954ac1 100644 > --- a/include/linux/iio/consumer.h > +++ b/include/linux/iio/consumer.h > @@ -399,6 +399,24 @@ int iio_read_channel_scale(struct iio_channel *chan, int *val, > int iio_multiply_value(int *result, s64 multiplier, > unsigned int type, int val, int val2); > > +/** > + * iio_divide_by_value() - Divide by an IIO value > + * @result: Destination pointer for the division result > + * @numerator: Numerator. > + * @type: One of the IIO_VAL_* constants. This decides how the @val > + * and @val2 parameters are interpreted. > + * @val: Denominator. > + * @val2: Denominator. @val2 use depends on type. > + * > + * Divide an s64 number by an IIO value, storing the result as > + * IIO_VAL_INT. This is typically used for scaling. > + * > + * Returns: > + * IIO_VAL_INT on success or a negative error-number on failure. > + */ > +int iio_divide_by_value(int *result, s64 numerator, > + unsigned int type, int val, int val2); > + > /** > * iio_convert_raw_to_processed() - Converts a raw value to a processed value > * @chan: The channel being queried > @@ -469,4 +487,22 @@ ssize_t iio_write_channel_ext_info(struct iio_channel *chan, const char *attr, > */ > ssize_t iio_read_channel_label(struct iio_channel *chan, char *buf); > > +/** > + * iio_write_channel_processed_scale() - scale and write processed value to a given channel > + * @chan: The channel being queried. > + * @val: Value to write. > + * @scale: Scale factor to apply during the conversion This could be more explicit about what sort of scaling this is. The function divides by this factor rather than multiplies by it. > + * > + * This function writes a processed value to a channel. A processed value means > + * that this value will have the correct unit and not some device internal > + * representation. If the device does not support writing a processed value, the > + * function will query the channel's scale and offset and write an appropriately > + * transformed raw value. > + * Could be helpful even if obvious to most people... Context: May sleep. > + * Return: an error code or 0. > + * > + */ > +int iio_write_channel_processed_scale(struct iio_channel *chan, int val, > + unsigned int scale); > + > #endif >