Re: [Patch v5 3/6] IIO: core: Modify scan element type

From: Jonathan Cameron
Date: Tue Apr 15 2014 - 01:52:41 EST



On April 14, 2014 11:33:12 PM GMT+01:00, Peter Meerwald <pmeerw@xxxxxxxxxx> wrote:
>> The current scan element type uses the following format:
>> [be|le]:[s|u]bits/storagebits[>>shift].
>> To specify multiple elements in this type, added a repeat value.
>> So new format is:
>> [be|le]:[s|u]bits/storagebits{X[repeat]}[>>shift].
>> Here X is specifying how may times, real/storage bits are repeating.
>>
>> When X is value is 0 or 1, then repeat value is not used in the
>format,
>> and it will be same as existing format.
>
>minor comments inline
>
>> ---
>> drivers/iio/industrialio-buffer.c | 41
>+++++++++++++++++++++++++++++++++------
>> include/linux/iio/iio.h | 9 +++++++++
>> 2 files changed, 44 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/iio/industrialio-buffer.c
>b/drivers/iio/industrialio-buffer.c
>> index e108f2a..aa90c68 100644
>> --- a/drivers/iio/industrialio-buffer.c
>> +++ b/drivers/iio/industrialio-buffer.c
>> @@ -150,7 +150,16 @@ static ssize_t iio_show_fixed_type(struct device
>*dev,
>> type = IIO_BE;
>> #endif
>> }
>> - return sprintf(buf, "%s:%c%d/%d>>%u\n",
>> + if (this_attr->c->scan_type.repeat > 1)
>> + return sprintf(buf, "%s:%c%d/%d{%d[repeat]}>>%u\n",
>> + iio_endian_prefix[type],
>> + this_attr->c->scan_type.sign,
>> + this_attr->c->scan_type.realbits,
>> + this_attr->c->scan_type.storagebits,
>> + this_attr->c->scan_type.repeat,
>> + this_attr->c->scan_type.shift);
>> + else
>> + return sprintf(buf, "%s:%c%d/%d>>%u\n",
>> iio_endian_prefix[type],
>> this_attr->c->scan_type.sign,
>> this_attr->c->scan_type.realbits,
>> @@ -474,14 +483,22 @@ static int iio_compute_scan_bytes(struct
>iio_dev *indio_dev,
>> for_each_set_bit(i, mask,
>> indio_dev->masklength) {
>> ch = iio_find_channel_from_si(indio_dev, i);
>> - length = ch->scan_type.storagebits / 8;
>> + if (ch->scan_type.repeat > 1)
>> + length = ch->scan_type.storagebits / 8 *
>> + ch->scan_type.repeat;
>
>so storagebits should be a multiple of 8 and != 0;
>we cannot have repeated groups of say 4 bits

Indeed not. Having unaligned data would probably prove more painful than using more
memory... Real requirements will be stricter as power of 2 multiples of bytes only.
This is in theory the plan for all buffer elements..
>
>> + else
>> + length = ch->scan_type.storagebits / 8;
>> bytes = ALIGN(bytes, length);
>> bytes += length;
>> }
>> if (timestamp) {
>> ch = iio_find_channel_from_si(indio_dev,
>> indio_dev->scan_index_timestamp);
>> - length = ch->scan_type.storagebits / 8;
>> + if (ch->scan_type.repeat > 1)
>> + length = ch->scan_type.storagebits / 8 *
>> + ch->scan_type.repeat;
>> + else
>> + length = ch->scan_type.storagebits / 8;
>> bytes = ALIGN(bytes, length);
>> bytes += length;
>> }
>> @@ -957,7 +974,11 @@ static int iio_buffer_update_demux(struct
>iio_dev *indio_dev,
>> indio_dev->masklength,
>> in_ind + 1);
>> ch = iio_find_channel_from_si(indio_dev, in_ind);
>> - length = ch->scan_type.storagebits/8;
>> + if (ch->scan_type.repeat > 1)
>> + length = ch->scan_type.storagebits / 8 *
>> + ch->scan_type.repeat;
>> + else
>> + length = ch->scan_type.storagebits / 8;
>> /* Make sure we are aligned */
>> in_loc += length;
>> if (in_loc % length)
>> @@ -969,7 +990,11 @@ static int iio_buffer_update_demux(struct
>iio_dev *indio_dev,
>> goto error_clear_mux_table;
>> }
>> ch = iio_find_channel_from_si(indio_dev, in_ind);
>> - length = ch->scan_type.storagebits/8;
>> + if (ch->scan_type.repeat > 1)
>> + length = ch->scan_type.storagebits / 8 *
>> + ch->scan_type.repeat;
>> + else
>> + length = ch->scan_type.storagebits / 8;
>> if (out_loc % length)
>> out_loc += length - out_loc % length;
>> if (in_loc % length)
>> @@ -990,7 +1015,11 @@ static int iio_buffer_update_demux(struct
>iio_dev *indio_dev,
>> }
>> ch = iio_find_channel_from_si(indio_dev,
>> indio_dev->scan_index_timestamp);
>> - length = ch->scan_type.storagebits/8;
>> + if (ch->scan_type.repeat > 1)
>> + length = ch->scan_type.storagebits / 8 *
>> + ch->scan_type.repeat;
>> + else
>> + length = ch->scan_type.storagebits / 8;
>> if (out_loc % length)
>> out_loc += length - out_loc % length;
>> if (in_loc % length)
>> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
>> index 5629c92..324ae00 100644
>> --- a/include/linux/iio/iio.h
>> +++ b/include/linux/iio/iio.h
>> @@ -177,6 +177,14 @@ struct iio_event_spec {
>> * shift: Shift right by this before masking out
>> * realbits.
>> * endianness: little or big endian
>> + * repeat: No. of times real/storage bits repeats.
>
>I'd rather spell out 'Number'
>
>> + * By default, when repeat is set to 0
>> + * repeat value is treated as 1. When
>> + * repeat value is 0 or 1, then there is
>> + * no change in existing scan element
>
>'no change in existing scan element' -- this makes sense only now
>
>maybe: 'When the repeat element is more than 1, then the type element
>in
>sysfs will show a repeat value. Otherwise, the number of repetitions is
>omitted.'
>
>> + * type, in sysfs. When set to more than
>
>no comma before 'in sysfs.'
>
>
>> + * 1, then the type element in sysfs will
>> + * show repeat value.
>> * @info_mask_separate: What information is to be exported that is
>specific to
>> * this channel.
>> * @info_mask_shared_by_type: What information is to be exported
>that is shared
>> @@ -219,6 +227,7 @@ struct iio_chan_spec {
>> u8 realbits;
>> u8 storagebits;
>> u8 shift;
>> + u8 repeat;
>> enum iio_endian endianness;
>> } scan_type;
>> long info_mask_separate;
>>

--
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