Re: [Patch v3 2/6] IIO: core: Introduce read_raw_multi

Jonathan Cameron
2014-04-14T21:02:07Z

On April 14, 2014 8:02:29 AM GMT+01:00, Jonathan Cameron <jic23@kernel.org> wrote:
>
>
>On April 14, 2014 2:51:22 AM GMT+01:00, Srinivas Pandruvada
><srinivas.pandruvada@linux.intel.com> wrote:
>>
>>On 04/12/2014 09:52 AM, Jonathan Cameron wrote:
>>> 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@linux.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.
>>>
>>I was thinking of using snprintf, but buf had no length passed. If we
>>assume PAGE_SIZE as max length
>>then I can do what you suggested below,
>IIRC sysfs buffers are always PAGE_SIZE long. Easy enough to check I
>guess.
Yup. See fs/sysfs/file.c
sysfs_kf_seq_show.

>>
>>Thanks,
>>Srinivas
>>> 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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