Hi Victor,
Below just a few very minor styling points. Sorry I didn't notice them
before. However, I am also fine with this version as it is.
Acked-by: Matteo Martelli <matteomartelli3@xxxxxxxxx>
On Fri, 15 Nov 2024 12:07:56 +0200, <victor.duicu@xxxxxxxxxxxxx> wrote:
> From: Victor Duicu <victor.duicu@xxxxxxxxxxxxx>
>
> This patch implements ACPI support to Microchip pac1921.
> The driver can read the shunt resistor value and label from the ACPI table.
>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Signed-off-by: Victor Duicu <victor.duicu@xxxxxxxxxxxxx>
> ---
>
> The patch was tested on minnowboard and sama5.
>
> Differences related to previous versions:
> v12:
> - in pac1921_match_acpi_device reformat the instructions that
> were over 80 characters width.
> - remove PAC1921_MAX_SHUNT_VALUE_uOHMS. Now the maximum acceptable value
> of shunt resistor is INT_MAX. In pac1921_write_shunt_resistor
> change the shunt check to respect the new limit and to avoid
> overflow in val * MICRO.
>
> v11:
> - credit Andy Shevchenko for code review.
>
> v10:
> - fix coding style mistakes.
> - add UL to PAC1921_MAX_SHUNT_VALUE_uOHMS.
> - edit comment in pac1921_write_shunt_resistor.
> - in pac1921_probe use is_acpi_device_node instead of
> ACPI_HANDLE.
>
> v9:
> - put limits.h in sorted order.
> - remove guid_parse and implement GUID_INIT.
> - remove pac1921_shunt_is_valid.
> - change maximum acceptable value of shunt resistor to 2146.999999.
> This change was made so the readings for dt and ACPI share
> the same range.
> With this value the maximum current that can be read is
> 0.1V / 2146.999999 = 46.576 uA
> If we use INT_MAX the maximum current is
> 0.1V / 2147.483647 = 46.566 uA
> The relative error between the two is 0.0214, so it is
> small enough to allow for code simplicity.
> A shunt value over a few hundred Ohms is quite unusual.
>
> v8:
> - fix multiple coding style errors.
> - in pac1921_match_acpi_device change error type to ENOMEM
> at label is NULL branch.
> - in pac1921_match_acpi_device when reading label,
> change accesing method of string.
> - change name of PAC1921_ACPI_GET_UOHMS_VALS to
> PAC1921_ACPI_GET_uOHMS_VALS.
> - add limits.h in include list.
> - change integer constant in PAC1921_MAX_SHUNT_VALUE_OHMS
> to INT_MAX / MICRO.
> - change pac1921_shunt_is_invalid to pac1921_shunt_is_valid.
> - in pac1921_match_acpi_device change name of variable rez to status.
>
> v7:
> - in pac1921_shunt_is_invalid remove brackets in return.
> - in pac1921_match_acpi_device and pac1921_parse_of_fw move checking of
> shunt value and scale calculation to pac1921_probe.
> - in pac1921_match_acpi_device change devm_kmemdup to devm_kstrdup
> and add label check for NULL.
> - in pac1921_match_acpi_device and pac1921_parse_of_fw remove unnecessary
> entry arguments. Now indio_dev is the only entry argument.
> - in pac1921_probe, pac1921_match_acpi_device and pac1921_parse_of_fw
> standardised structure accesing.
>
> v6:
> - set maximum acceptable value of shunt resistor to INT_MAX UOHMS
> in devicetree, ACPI table and user input.
> - in pac1921_match_acpi_device remove temp variable.
>
> v5:
> - set maximum acceptable value of shunt resistor to 2KOHM in devicetree,
> ACPI table and user input. The chosen value is lesser than INT_MAX,
> which is about 2.1KOHM.
> - in pac1921_match_acpi_device and pac1921_parse_of_fw change to only
> read 32b values for resistor shunt.
>
> v4:
> - change name of pac1921_shunt_is_valid to pac1921_shunt_is_invalid.
> - fix coding style.
> - in pac1921_parse_of_fw change back to device_property_read_u32.
>
> v3:
> - simplify and make inline function pac1921_shunt_is_valid. Make argument u64.
> - fix link to DSM documentation.
> - in pac1921_match_acpi_device and pac1921_parse_of_fw, the shunt value is
> read as u64.
> - in pac1921_parse_of_fw remove code for reading label value from
> devicetree.
> - in pac1921_write_shunt_resistor cast the multiply result to u64 in order
> to fix overflow.
>
> v2:
> - remove name variable from priv. Driver reads label attribute with
> sysfs.
> - define pac1921_shunt_is_valid function.
> - move default assignments in pac1921_probe to original position.
> - roll back coding style changes.
> - add documentation for DSM(the linked document was used as reference).
> - remove acpi_match_device in pac1921_match_acpi_device.
> - remove unnecessary null assignment and comment.
> - change name of function pac1921_match_of_device to
> pac1921_parse_of_fw.
>
> v1:
> - initial version for review.
>
> drivers/iio/adc/pac1921.c | 100 ++++++++++++++++++++++++++++++++++----
> 1 file changed, 90 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iio/adc/pac1921.c b/drivers/iio/adc/pac1921.c
> index b0f6727cfe38..a78ae34057a1 100644
> --- a/drivers/iio/adc/pac1921.c
> +++ b/drivers/iio/adc/pac1921.c
> @@ -12,6 +12,7 @@
> #include <linux/iio/iio.h>
> #include <linux/iio/trigger_consumer.h>
> #include <linux/iio/triggered_buffer.h>
> +#include <linux/limits.h>
> #include <linux/regmap.h>
> #include <linux/units.h>
>
> @@ -67,6 +68,14 @@ enum pac1921_mxsl {
> #define PAC1921_DEFAULT_DI_GAIN 0 /* 2^(value): 1x gain (HW default) */
> #define PAC1921_DEFAULT_NUM_SAMPLES 0 /* 2^(value): 1 sample (HW default) */
>
> +#define PAC1921_ACPI_GET_uOHMS_VALS 0
> +#define PAC1921_ACPI_GET_LABEL 1
> +
> +/* f7bb9932-86ee-4516-a236-7a7a742e55cb */
> +static const guid_t pac1921_guid =
> + GUID_INIT(0xf7bb9932, 0x86ee, 0x4516, 0xa2,
> + 0x36, 0x7a, 0x7a, 0x74, 0x2e, 0x55, 0xcb);
> +
> /*
> * Pre-computed scale factors for BUS voltage
> * format: IIO_VAL_INT_PLUS_NANO
> @@ -782,7 +791,7 @@ static ssize_t pac1921_write_shunt_resistor(struct iio_dev *indio_dev,
> const char *buf, size_t len)
> {
> struct pac1921_priv *priv = iio_priv(indio_dev);
> - u64 rshunt_uohm;
> + u32 rshunt_uohm;
> int val, val_fract;
> int ret;
>
> @@ -793,10 +802,17 @@ static ssize_t pac1921_write_shunt_resistor(struct iio_dev *indio_dev,
> if (ret)
> return ret;
>
> - rshunt_uohm = val * MICRO + val_fract;
> - if (rshunt_uohm == 0 || rshunt_uohm > INT_MAX)
> + /*
> + * This check validates the shunt is not zero and does not surpass
> + * INT_MAX. The check is done before calculating in order to avoid
> + * val * MICRO overflowing.
> + */
> + if ((!val && !val_fract) || (val > INT_MAX / MICRO) ||
> + ((val == INT_MAX / MICRO) && (val_fract > INT_MAX % MICRO)))
> return -EINVAL;
Can the unnecessary parenthesis be removed?
if ((!val && !val_fract) || (val > INT_MAX / MICRO) ||
^.....................^
((val == INT_MAX / MICRO) && (val_fract > INT_MAX % MICRO)))
^......................^ ^...........................^
>
> + rshunt_uohm = val * MICRO + val_fract;
> +
> guard(mutex)(&priv->lock);
>
> priv->rshunt_uohm = rshunt_uohm;
> @@ -1151,6 +1167,61 @@ static void pac1921_regulator_disable(void *data)
> regulator_disable(regulator);
> }
>
> +/*
> + * Documentation related to the ACPI device definition
> + * https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ApplicationNotes/ApplicationNotes/PAC193X-Integration-Notes-for-Microsoft-Windows-10-and-Windows-11-Driver-Support-DS00002534.pdf
> + */
> +static int pac1921_match_acpi_device(struct iio_dev *indio_dev)
> +{
> + acpi_handle handle;
> + union acpi_object *status;
> + char *label;
> + struct pac1921_priv *priv = iio_priv(indio_dev);
> + struct device *dev = &priv->client->dev;
> +
> + handle = ACPI_HANDLE(dev);
> +
> + status = acpi_evaluate_dsm(handle, &pac1921_guid, 1,
> + PAC1921_ACPI_GET_uOHMS_VALS, NULL);
> + if (!status)
> + return dev_err_probe(dev, -EINVAL,
> + "Could not read shunt from ACPI table\n");
> +
> + priv->rshunt_uohm = status->package.elements[0].integer.value;
> + ACPI_FREE(status);
> +
> + status = acpi_evaluate_dsm(handle, &pac1921_guid, 1,
> + PAC1921_ACPI_GET_LABEL, NULL);
> + if (!status)
> + return dev_err_probe(dev, -EINVAL,
> + "Could not read label from ACPI table\n");
> +
> + label = devm_kstrdup(dev, status->package.elements[0].string.pointer,
> + GFP_KERNEL);
> + if (!label)
> + return -ENOMEM;
> +
> + indio_dev->label = label;
> + ACPI_FREE(status);
> +
> + return 0;
> +}
> +
> +static int pac1921_parse_of_fw(struct iio_dev *indio_dev)
> +{
> + int ret;
> + struct pac1921_priv *priv = iio_priv(indio_dev);
> + struct device *dev = &priv->client->dev;
> +
> + ret = device_property_read_u32(dev, "shunt-resistor-micro-ohms",
> + &priv->rshunt_uohm);
> + if (ret)
> + return dev_err_probe(dev, ret,
> + "Cannot read shunt resistor property\n");
> +
> + return 0;
> +}
> +
> static int pac1921_probe(struct i2c_client *client)
> {
> struct device *dev = &client->dev;
> @@ -1179,14 +1250,16 @@ static int pac1921_probe(struct i2c_client *client)
> priv->di_gain = PAC1921_DEFAULT_DI_GAIN;
> priv->n_samples = PAC1921_DEFAULT_NUM_SAMPLES;
>
> - ret = device_property_read_u32(dev, "shunt-resistor-micro-ohms",
> - &priv->rshunt_uohm);
> - if (ret)
> + if (is_acpi_device_node(dev->fwnode))
> + ret = pac1921_match_acpi_device(indio_dev);
> + else
> + ret = pac1921_parse_of_fw(indio_dev);
> + if (ret < 0)
For consistency: if (ret) instead of if (ret < 0)
> return dev_err_probe(dev, ret,
> - "Cannot read shunt resistor property\n");
> - if (priv->rshunt_uohm == 0 || priv->rshunt_uohm > INT_MAX)
> - return dev_err_probe(dev, -EINVAL,
> - "Invalid shunt resistor: %u\n",
> + "Parameter parsing error\n");
> +
> + if (!priv->rshunt_uohm || priv->rshunt_uohm > INT_MAX)
> + return dev_err_probe(dev, -EINVAL, "Invalid shunt resistor: %u\n",
The error string in a new line to keep it 80 char wide.
> priv->rshunt_uohm);
>
> pac1921_calc_current_scales(priv);
> @@ -1246,11 +1319,18 @@ static const struct of_device_id pac1921_of_match[] = {
> };
> MODULE_DEVICE_TABLE(of, pac1921_of_match);
>
> +static const struct acpi_device_id pac1921_acpi_match[] = {
> + { "MCHP1921" },
> + { }
> +};
> +MODULE_DEVICE_TABLE(acpi, pac1921_acpi_match);
> +
> static struct i2c_driver pac1921_driver = {
> .driver = {
> .name = "pac1921",
> .pm = pm_sleep_ptr(&pac1921_pm_ops),
> .of_match_table = pac1921_of_match,
> + .acpi_match_table = pac1921_acpi_match,
> },
> .probe = pac1921_probe,
> .id_table = pac1921_id,
>
> base-commit: 20fd1383cd616d61b2a79967da1221dc6cfb8430
> --
> 2.43.0
>
Thanks,
Matteo Martelli
