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SubjectRe: [PATCH v4 3/3] iio: magnetometer: Add driver support for PNI RM3100
Date

On 2018/10/13 下午6:19, Jonathan Cameron wrote:
> On Fri, 12 Oct 2018 15:35:36 +0800
> Song Qiang<songqiang1304521@gmail.com> wrote:
>
>> PNI RM3100 is a high resolution, large signal immunity magnetometer,
>> composed of 3 single sensors and a processing chip with a MagI2C
>> interface.
>>
>> Following functions are available:
>> - Single-shot measurement from
>> /sys/bus/iio/devices/iio:deviceX/in_magn_{axis}_raw
>> - Triggerd buffer measurement.
>> - DRDY pin for data ready trigger.
>> - Both i2c and spi interface are supported.
>> - Both interrupt and polling measurement is supported, depends on if
>> the 'interrupts' in DT is declared.
>>
>> Signed-off-by: Song Qiang<songqiang1304521@gmail.com>
> A few questions for you (getting very close to being good to go btw!)
>
> Why do we have the 3second additional wait for conversions? I know we
> rarely wait that long, but still seems excessive.
>
> Few more comments inline.
>
> Thanks,
>
> Jonathan

Hi Jonathan,


The measurement time of this device varies from 1.7ms to 13 seconds, 3 seconds
is just a number in the middle between them. This may be worth discussing,
hoping to get a better solution from the community.


>> ---
>> MAINTAINERS | 7 +
>> drivers/iio/magnetometer/Kconfig | 29 ++
>> drivers/iio/magnetometer/Makefile | 4 +
>> drivers/iio/magnetometer/rm3100-core.c | 627 +++++++++++++++++++++++++
>> drivers/iio/magnetometer/rm3100-i2c.c | 58 +++
>> drivers/iio/magnetometer/rm3100-spi.c | 64 +++
>> drivers/iio/magnetometer/rm3100.h | 17 +
>> 7 files changed, 806 insertions(+)
>> create mode 100644 drivers/iio/magnetometer/rm3100-core.c
>> create mode 100644 drivers/iio/magnetometer/rm3100-i2c.c
>> create mode 100644 drivers/iio/magnetometer/rm3100-spi.c
>> create mode 100644 drivers/iio/magnetometer/rm3100.h
>>

...

>
>> +static irqreturn_t rm3100_trigger_handler(int irq, void *p)
>> +{
>> + struct iio_poll_func *pf = p;
>> + struct iio_dev *indio_dev = pf->indio_dev;
>> + unsigned long scan_mask = *indio_dev->active_scan_mask;
>> + unsigned int mask_len = indio_dev->masklength;
>> + struct rm3100_data *data = iio_priv(indio_dev);
>> + struct regmap *regmap = data->regmap;
>> + int ret, i, bit;
>> +
>> + mutex_lock(&data->lock);
>> + switch (scan_mask) {
>> + case BIT(0) | BIT(1) | BIT(2):
>> + ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 9);
>> + mutex_unlock(&data->lock);
>> + if (ret < 0)
>> + goto done;
>> + break;
>> + case BIT(0) | BIT(1):
>> + ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 6);
>> + mutex_unlock(&data->lock);
>> + if (ret < 0)
>> + goto done;
>> + break;
>> + case BIT(1) | BIT(2):
>> + ret = regmap_bulk_read(regmap, RM3100_REG_MY2, data->buffer, 6);
>> + mutex_unlock(&data->lock);
>> + if (ret < 0)
>> + goto done;
>> + break;
> What about BIT(0) | BIT(2)?
>
> Now you can do it like you have here and on that one corner case let the iio core
> demux code take care of it, but then you will need to provide available_scan_masks
> so the core knows it needs to handle this case.
>

This confused me a little. The available_scan_masks I was using is {BIT(0) |
BIT(1) | BIT(2), 0x0}. Apparently in this version of patch I would like it to
handle every circumstances like BIT(0), BIT(0) | BIT(2), BIT(1) | BIT(2), etc.
Since Phil mentioned he would like this to reduce bus usage as much as we can
and I want it, too, I think these three circumstances can be read consecutively
while others can be read one axis at a time. So I plan to let  BIT(0) | BIT(2)
fall into the 'default' section, which reads axis one by one.

My question is, since this handles every possible combination, do I still need
to list every available scan masks in available_scan_masks?


All other problems will be fixed in the next patch.

yours,

Song Qiang


...

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