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Message-ID: <53496F52.9040802@kernel.org>
Date: Sat, 12 Apr 2014 17:52:34 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
CC: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v3 2/6] IIO: core: Introduce read_raw_multi
On 09/04/14 01:56, Srinivas Pandruvada wrote:
> This callback is introduced to overcome some limitations of existing
> read_raw callback. The functionality of both existing read_raw and
> read_raw_multi is similar, both are used to request values from the
> device. The current read_raw callback allows only two return values.
> The new read_raw_multi allows returning multiple values. Instead of
> passing just address of val and val2, it passes length and pointer
> to values. Depending on the type and length of passed buffer, iio
> client drivers can return multiple values.
>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Hi Srinivas.
This has come together pretty much how I thought it would. Very nice.
Only comment inline is that I'd prefer we took care now with possiblity
of really long sets of values so that we don't get bitten by it sometime
in the future.
If you want to drop the reference to 0 having special meaning in the
comment as well, thats fine by me.
Jonathan
> ---
> drivers/iio/iio_core.h | 2 +-
> drivers/iio/industrialio-core.c | 65 ++++++++++++++++++++++++++--------------
> drivers/iio/industrialio-event.c | 6 ++--
> drivers/iio/inkern.c | 16 ++++++++--
> include/linux/iio/iio.h | 17 +++++++++++
> include/linux/iio/types.h | 1 +
> 6 files changed, 80 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
> index f6db6af..30327ad 100644
> --- a/drivers/iio/iio_core.h
> +++ b/drivers/iio/iio_core.h
> @@ -35,7 +35,7 @@ int __iio_add_chan_devattr(const char *postfix,
> struct list_head *attr_list);
> void iio_free_chan_devattr_list(struct list_head *attr_list);
>
> -ssize_t iio_format_value(char *buf, unsigned int type, int val, int val2);
> +ssize_t iio_format_value(char *buf, unsigned int type, int size, int *val);
>
> /* Event interface flags */
> #define IIO_BUSY_BIT_POS 1
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index ede16aec..3bd565c 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -373,41 +373,53 @@ EXPORT_SYMBOL_GPL(iio_enum_write);
> * @buf: The buffer to which the formated value gets written
> * @type: One of the IIO_VAL_... constants. This decides how the val and val2
> * parameters are formatted.
> - * @val: First part of the value, exact meaning depends on the type parameter.
> - * @val2: Second part of the value, exact meaning depends on the type parameter.
> + * @vals: pointer to the values, exact meaning depends on the type parameter.
> */
> -ssize_t iio_format_value(char *buf, unsigned int type, int val, int val2)
> +ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)
> {
> unsigned long long tmp;
> bool scale_db = false;
>
> switch (type) {
> case IIO_VAL_INT:
> - return sprintf(buf, "%d\n", val);
> + return sprintf(buf, "%d\n", vals[0]);
> case IIO_VAL_INT_PLUS_MICRO_DB:
> scale_db = true;
> case IIO_VAL_INT_PLUS_MICRO:
> - if (val2 < 0)
> - return sprintf(buf, "-%ld.%06u%s\n", abs(val), -val2,
> + if (vals[1] < 0)
> + return sprintf(buf, "-%ld.%06u%s\n", abs(vals[0]),
> + -vals[1],
> scale_db ? " dB" : "");
> else
> - return sprintf(buf, "%d.%06u%s\n", val, val2,
> + return sprintf(buf, "%d.%06u%s\n", vals[0], vals[1],
> scale_db ? " dB" : "");
> case IIO_VAL_INT_PLUS_NANO:
> - if (val2 < 0)
> - return sprintf(buf, "-%ld.%09u\n", abs(val), -val2);
> + if (vals[1] < 0)
> + return sprintf(buf, "-%ld.%09u\n", abs(vals[0]),
> + -vals[1]);
> else
> - return sprintf(buf, "%d.%09u\n", val, val2);
> + return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
> case IIO_VAL_FRACTIONAL:
> - tmp = div_s64((s64)val * 1000000000LL, val2);
> - val2 = do_div(tmp, 1000000000LL);
> - val = tmp;
> - return sprintf(buf, "%d.%09u\n", val, val2);
> + tmp = div_s64((s64)vals[0] * 1000000000LL, vals[1]);
> + vals[1] = do_div(tmp, 1000000000LL);
> + vals[0] = tmp;
> + return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
> case IIO_VAL_FRACTIONAL_LOG2:
> - tmp = (s64)val * 1000000000LL >> val2;
> - val2 = do_div(tmp, 1000000000LL);
> - val = tmp;
> - return sprintf(buf, "%d.%09u\n", val, val2);
> + tmp = (s64)vals[0] * 1000000000LL >> vals[1];
> + vals[1] = do_div(tmp, 1000000000LL);
> + vals[0] = tmp;
> + return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
> + case IIO_VAL_INT_MULTIPLE:
> + {
> + int i;
> + int len = 0;
> +
> + for (i = 0; i < size; ++i)
> + len += sprintf(&buf[len], "%d ", vals[i]);
> + buf[len++] = '\n';
> + buf[len++] = '\0';
Whilst we know this is of a fixed maxium length, I think we
want to take more care to ensure that we don't overrun the maximum
sysfs length. I'd also prefer specific use of snprintf for the new
line as well to make sure that doesn't cause trouble. i.e.
for (i = 0; i < size; ++i)
len += snprintf(&buf[len], PAGE_SIZE - len, "%d ", vals[i]);
len += snprintf(&buf[len], PAGE_SIZE - len, "/n");
The reasoning being that we could easily mess something up and hit these
limits sometime in the future. Also not using the explicit character
settting, but doing it with snprintf is easier to read (slightly ;)
> + return len;
> + }
> default:
> return 0;
> }
> @@ -419,14 +431,23 @@ static ssize_t iio_read_channel_info(struct device *dev,
> {
> struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> - int val, val2;
> - int ret = indio_dev->info->read_raw(indio_dev, this_attr->c,
> - &val, &val2, this_attr->address);
> + int vals[INDIO_MAX_RAW_ELEMENTS];
> + int ret;
> + int val_len = 2;
> +
> + if (indio_dev->info->read_raw_multi)
> + ret = indio_dev->info->read_raw_multi(indio_dev, this_attr->c,
> + INDIO_MAX_RAW_ELEMENTS,
> + vals, &val_len,
> + this_attr->address);
> + else
> + ret = indio_dev->info->read_raw(indio_dev, this_attr->c,
> + &vals[0], &vals[1], this_attr->address);
>
> if (ret < 0)
> return ret;
>
> - return iio_format_value(buf, ret, val, val2);
> + return iio_format_value(buf, ret, val_len, vals);
> }
>
> /**
> diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
> index ea6e06b..1b4f31b 100644
> --- a/drivers/iio/industrialio-event.c
> +++ b/drivers/iio/industrialio-event.c
> @@ -270,7 +270,7 @@ static ssize_t iio_ev_value_show(struct device *dev,
> {
> struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> - int val, val2;
> + int val, val2, val_arr[2];
> int ret;
>
> ret = indio_dev->info->read_event_value(indio_dev,
> @@ -279,7 +279,9 @@ static ssize_t iio_ev_value_show(struct device *dev,
> &val, &val2);
> if (ret < 0)
> return ret;
> - return iio_format_value(buf, ret, val, val2);
> + val_arr[0] = val;
> + val_arr[1] = val2;
> + return iio_format_value(buf, ret, 2, val_arr);
> }
>
> static ssize_t iio_ev_value_store(struct device *dev,
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index 0cf5f8e..75e5386 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -417,12 +417,24 @@ static int iio_channel_read(struct iio_channel *chan, int *val, int *val2,
> enum iio_chan_info_enum info)
> {
> int unused;
> + int vals[INDIO_MAX_RAW_ELEMENTS];
> + int ret;
> + int val_len = 2;
>
> if (val2 == NULL)
> val2 = &unused;
>
> - return chan->indio_dev->info->read_raw(chan->indio_dev, chan->channel,
> - val, val2, info);
> + if (chan->indio_dev->info->read_raw_multi) {
> + ret = chan->indio_dev->info->read_raw_multi(chan->indio_dev,
> + chan->channel, INDIO_MAX_RAW_ELEMENTS,
> + vals, &val_len, info);
> + *val = vals[0];
> + *val2 = vals[1];
> + } else
> + ret = chan->indio_dev->info->read_raw(chan->indio_dev,
> + chan->channel, val, val2, info);
> +
> + return ret;
> }
>
> int iio_read_channel_raw(struct iio_channel *chan, int *val)
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index 5f2d00e..5629c92 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -288,6 +288,8 @@ static inline s64 iio_get_time_ns(void)
> #define INDIO_ALL_BUFFER_MODES \
> (INDIO_BUFFER_TRIGGERED | INDIO_BUFFER_HARDWARE)
>
> +#define INDIO_MAX_RAW_ELEMENTS 4
> +
> struct iio_trigger; /* forward declaration */
> struct iio_dev;
>
> @@ -302,6 +304,14 @@ struct iio_dev;
> * the channel in question. Return value will specify the
> * type of value returned by the device. val and val2 will
> * contain the elements making up the returned value.
> + * @read_raw_multi: function to return values from the device.
> + * mask specifies which value. Note 0 means a reading of
This note 0 bit wants to go now it is much more explicit in the way the code
works, but leave it here for now and we can tidy up both this and the read_raw
callback at the same time.
> + * the channel in question. Return value will specify the
> + * type of value returned by the device. vals pointer
> + * contain the elements making up the returned value.
> + * max_len specifies maximum number of elements
> + * vals pointer can contain. val_len is used to return
> + * length of valid elements in vals.
> * @write_raw: function to write a value to the device.
> * Parameters are the same as for read_raw.
> * @write_raw_get_fmt: callback function to query the expected
> @@ -328,6 +338,13 @@ struct iio_info {
> int *val2,
> long mask);
>
> + int (*read_raw_multi)(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int max_len,
> + int *vals,
> + int *val_len,
> + long mask);
> +
> int (*write_raw)(struct iio_dev *indio_dev,
> struct iio_chan_spec const *chan,
> int val,
> diff --git a/include/linux/iio/types.h b/include/linux/iio/types.h
> index 084d882..a13c224 100644
> --- a/include/linux/iio/types.h
> +++ b/include/linux/iio/types.h
> @@ -79,6 +79,7 @@ enum iio_event_direction {
> #define IIO_VAL_INT_PLUS_MICRO 2
> #define IIO_VAL_INT_PLUS_NANO 3
> #define IIO_VAL_INT_PLUS_MICRO_DB 4
> +#define IIO_VAL_INT_MULTIPLE 5
> #define IIO_VAL_FRACTIONAL 10
> #define IIO_VAL_FRACTIONAL_LOG2 11
>
>
--
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