Message-ID: <549D55E2.5000906@kernel.org>
Date:	Fri, 26 Dec 2014 12:34:42 +0000
From:	Jonathan Cameron <jic23@...nel.org>
To:	Karol Wrona <k.wrona@...sung.com>, linux-iio@...r.kernel.org,
	Hartmut Knaack <knaack.h@....de>, linux-kernel@...r.kernel.org
CC:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Karol Wrona <wrona.vy@...il.com>
Subject: Re: [PATCH v3 4/5] iio: common: ssp_sensors: Add sensorhub accelerometer
 sensor

On 08/12/14 10:41, Karol Wrona wrote:
> On 12/06/2014 03:52 PM, Jonathan Cameron wrote:
>> On 05/12/14 19:54, Karol Wrona wrote:
>>> This patch adds accelerometer iio driver which uses sensorhub as data
>>> provider.
>>>
>>> Change-Id: I4686741b7401ec5cbf4b5d0f2a5cc146fbe24d53
>>> Signed-off-by: Karol Wrona <k.wrona@...sung.com>
>>> Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
>>> ---
>>>   drivers/iio/accel/Makefile           |    1 +
>>>   drivers/iio/accel/ssp_accel_sensor.c |  203 ++++++++++++++++++++++++++++++++++
>>>   2 files changed, 204 insertions(+)
>>>   create mode 100644 drivers/iio/accel/ssp_accel_sensor.c
>>>
>>> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
>>> index a593996..df6a0b2 100644
>>> --- a/drivers/iio/accel/Makefile
>>> +++ b/drivers/iio/accel/Makefile
>>> @@ -9,6 +9,7 @@ obj-$(CONFIG_HID_SENSOR_ACCEL_3D) += hid-sensor-accel-3d.o
>>>   obj-$(CONFIG_KXCJK1013) += kxcjk-1013.o
>>>   obj-$(CONFIG_KXSD9)    += kxsd9.o
>>>   obj-$(CONFIG_MMA8452)    += mma8452.o
>>> +obj-$(CONFIG_IIO_SSP_SENSOR) += ssp_accel_sensor.o
>>>
>>>   obj-$(CONFIG_IIO_ST_ACCEL_3AXIS) += st_accel.o
>>>   st_accel-y := st_accel_core.o
>>> diff --git a/drivers/iio/accel/ssp_accel_sensor.c b/drivers/iio/accel/ssp_accel_sensor.c
>>> new file mode 100644
>>> index 0000000..0a47c29
>>> --- /dev/null
>>> +++ b/drivers/iio/accel/ssp_accel_sensor.c
>>> @@ -0,0 +1,203 @@
>>> +/*
>>> + *  Copyright (C) 2014, Samsung Electronics Co. Ltd. All Rights Reserved.
>>> + *
>>> + *  This program is free software; you can redistribute it and/or modify
>>> + *  it under the terms of the GNU General Public License as published by
>>> + *  the Free Software Foundation; either version 2 of the License, or
>>> + *  (at your option) any later version.
>>> + *
>>> + *  This program is distributed in the hope that it will be useful,
>>> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> + *  GNU General Public License for more details.
>>> + *
>>> + */
>>> +
>>> +#include <linux/iio/common/ssp_sensors.h>
>>> +#include <linux/iio/iio.h>
>>> +#include <linux/iio/kfifo_buf.h>
>>> +#include <linux/module.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/slab.h>
>>> +#include "../common/ssp_sensors/ssp_iio_sensor.h"
>>> +
>>> +#define SSP_CHANNEL_COUNT 3
>>> +
>>> +#define SSP_ACCEL_NAME "ssp-accelerometer"
>>> +static const char ssp_accel_device_name[] = SSP_ACCEL_NAME;
>>> +
>>> +enum ssp_accel_3d_channel {
>>> +    SSP_CHANNEL_SCAN_INDEX_X,
>>> +    SSP_CHANNEL_SCAN_INDEX_Y,
>>> +    SSP_CHANNEL_SCAN_INDEX_Z,
>>> +    SSP_CHANNEL_SCAN_INDEX_TIME,
>>> +    SSP_ACCEL_3D_CHANNEL_MAX,
>> you don't actually use this max element so drop it.
>>> +};
>>> +
>>> +static int ssp_accel_read_raw(struct iio_dev *indio_dev,
>>> +                  struct iio_chan_spec const *chan,  int *val,
>>> +                  int *val2, long mask)
>>> +{
>>> +    u32 t;
>>> +    struct ssp_data *data = dev_get_drvdata(indio_dev->dev.parent->parent);
>>> +
>>> +    switch (mask) {
>>> +    case IIO_CHAN_INFO_SAMP_FREQ:
>>> +        t = ssp_get_sensor_delay(data, SSP_ACCELEROMETER_SENSOR);
>>> +        ssp_convert_to_freq(t, val, val2);
>>> +        return IIO_VAL_INT_PLUS_MICRO;
>>> +    default:
>>> +        break;
>>> +    }
>>> +
>>> +    return -EINVAL;
>>> +}
>>> +
>>> +static int ssp_accel_write_raw(struct iio_dev *indio_dev,
>>> +                   struct iio_chan_spec const *chan, int val,
>>> +                   int val2, long mask)
>>> +{
>>> +    int ret;
>>> +    struct ssp_data *data = dev_get_drvdata(indio_dev->dev.parent->parent);
>>> +
>>> +    switch (mask) {
>>> +    case IIO_CHAN_INFO_SAMP_FREQ:
>>> +        ret = ssp_convert_to_time(val, val2);
>>> +        ret = ssp_change_delay(data, SSP_ACCELEROMETER_SENSOR, ret);
>>> +        if (ret < 0)
>>> +            dev_err(&indio_dev->dev, "accel sensor enable fail\n");
>>> +
>>> +        return ret;
>>> +    default:
>>> +        break;
>>> +    }
>>> +
>>> +    return -EINVAL;
>>> +}
>>> +
>>> +static struct iio_info ssp_accel_iio_info = {
>>> +    .read_raw = &ssp_accel_read_raw,
>>> +    .write_raw = &ssp_accel_write_raw,
>>> +};
>>> +
>>> +static const struct iio_chan_spec ssp_acc_channels[] = {
>>> +    SSP_CHANNEL_AG(IIO_ACCEL, IIO_MOD_X, SSP_CHANNEL_SCAN_INDEX_X),
>>> +    SSP_CHANNEL_AG(IIO_ACCEL, IIO_MOD_Y, SSP_CHANNEL_SCAN_INDEX_Y),
>>> +    SSP_CHANNEL_AG(IIO_ACCEL, IIO_MOD_Z, SSP_CHANNEL_SCAN_INDEX_Z),
>>> +    IIO_CHAN_SOFT_TIMESTAMP(SSP_CHANNEL_SCAN_INDEX_TIME),
>> hmm. Not actually a soft timestamp so I guess we should really rename that
>> macro.  Actually is your resulting timestamp 32 bit?  If so you could
>> specify the channel as such and include a scale to allow userspace to
>> convert it as it wishes.
> Ok, I will rethink that.  This timestamp is 64-bit and it is system time
> plus diff taken from sample but I would have relative time at all on 32-bit.
>>> +};
>>> +
>>> +static int ssp_process_accel_data(struct iio_dev *indio_dev, void *buf,
>>> +                  int64_t timestamp)
>> We could hang a set of triggers of the parent device and use the in
>> conjunction with some local buffering to fire off the children.
>> There would be the advantage that we could trigger other sensors off them
>> (to get roughly synchronized additional signals).  Probably not worth it
>> though but I thought I'd mention the option.
>>> +{
>>> +    __le32 time;
>>> +    const int len = SSP_ACCELEROMETER_SIZE;
>>> +    int64_t calculated_time;
>>> +    char *data;
>>> +    int ret;
>>> +
>>> +    if (indio_dev->scan_bytes == 0)
>>> +        return 0;
>>> +
>>> +    data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
>>> +    if (!data)
>>> +        return -ENOMEM;
>> I'd allocate this in your iio_priv structure and setup the length in preenable
>> etc.  Last thing we want in here is to waste time with a memory allocation and
>> free.
> You are right. Generally for commands in ssp_spi.c these allocation won't hurt but here I created a pure waste..
>>> +
>>> +    memcpy(data, buf, len);
>> It's a little uggly but I think you can avoid the copy if the timestamp
>> isn't in use (as then we don't need the additional space).
>>> +
>>> +    if (indio_dev->scan_timestamp) {
>>> +        memcpy(&time, &((char *)buf)[len], SSP_TIME_SIZE);
>>> +        calculated_time =
>>> +            timestamp + (int64_t)le32_to_cpu(time) * 1000000;
>> Cool - our first hardware supplied timestamp ;)
>>> +    }
>>> +
>>> +    ret = iio_push_to_buffers_with_timestamp(indio_dev, data,
>>> +                         calculated_time);
>>> +
>>> +    kfree(data);
>>> +
>>> +    return ret;
>>> +}
>>> +
>>> +static const struct iio_buffer_setup_ops ssp_accel_buffer_ops = {
>>> +    .postenable = &ssp_common_buffer_postenable,
>>> +    .predisable = &ssp_common_buffer_predisable,
>>> +};
>>> +
>>> +static int ssp_accel_probe(struct platform_device *pdev)
>>> +{
>>> +    int ret;
>>> +    struct iio_dev *indio_dev;
>>> +    struct ssp_sensor_data *spd;
>>> +
>>> +    indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*spd));
>>> +    if (!indio_dev)
>>> +        return -ENOMEM;
>>> +
>>> +    spd = iio_priv(indio_dev);
>>> +
>>> +    spd->process_data = ssp_process_accel_data;
>>> +    spd->type = SSP_ACCELEROMETER_SENSOR;
>>> +
>>> +    indio_dev->name = ssp_accel_device_name;
>>> +    indio_dev->dev.parent = &pdev->dev;
>>> +    indio_dev->dev.of_node = pdev->dev.of_node;
>>> +    indio_dev->info = &ssp_accel_iio_info;
>>> +    indio_dev->modes = INDIO_BUFFER_HARDWARE;
>> hmm. A rare beast with no polled access.  But is it actually a hardware
>> buffer?  Doesn't look that much like one.  I think we may need a more
>> refined set of options for the buffer type.
> Here I'm confused. Do you mean a new buffer type in IIO?
Yup. Just suggested the same in a review of an ACPI ALS driver.
We'd currently handle it exactly the same as a hardware buffer
but without the current naming (and with the potential to do
it differently if needed in future).

>>
>>> +    indio_dev->channels = ssp_acc_channels;
>>> +    indio_dev->num_channels = ARRAY_SIZE(ssp_acc_channels);
>>> +
>>> +    ret = ssp_common_setup_buffer(indio_dev, &ssp_accel_buffer_ops);
>>> +    if (ret < 0) {
>>> +        dev_err(&pdev->dev, "Buffer setup fail\n");
>>> +        return ret;
>>> +    }
>>> +
>>> +    platform_set_drvdata(pdev, indio_dev);
>>> +
>>> +    ret = iio_device_register(indio_dev);
>>> +    if (ret < 0) {
>>> +        iio_buffer_unregister(indio_dev);
>>> +        iio_kfifo_free(indio_dev->buffer);
>>> +        return ret;
>>> +    }
>>> +
>>> +    /* need to be really sure about success for this one */
>> err, what does the comment mean?
> this only adds ptr to the table so I wanted to assure that it should be done after ii_device_register, maybe this is too obvious to comment.
I'd just expand on the comment a little.
something like - /* As this registers for data flow, we need to be sure it is after all other setup */
>>> +    ssp_register_consumer(indio_dev, SSP_ACCELEROMETER_SENSOR);
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static int ssp_accel_remove(struct platform_device *pdev)
>>> +{
>>> +    struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>>> +
>>> +    iio_device_unregister(indio_dev);
>>> +    iio_buffer_unregister(indio_dev);
>>> +    iio_kfifo_free(indio_dev->buffer);
>> Feels rather like we need a devm_iio_kfifo_alloc
>> Actually, as you are wrapping the allocation, I'd prefer you have
>> an obviously matched cleanup function to ssp_common_setup_buffer
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static const struct of_device_id ssp_accel_id_table[] = {
>>> +    {
>>> +        .compatible = "samsung,mpu6500-accel",
>>> +    },
>>> +    {},
>>> +};
>>> +
>>> +static struct platform_driver ssp_accel_driver = {
>>> +    .driver = {
>>> +        .owner = THIS_MODULE,
>>> +        .name = SSP_ACCEL_NAME,
>>> +        .of_match_table = ssp_accel_id_table,
>>> +    },
>>> +    .probe = ssp_accel_probe,
>>> +    .remove =  ssp_accel_remove,
>>> +};
>>> +
>>> +module_platform_driver(ssp_accel_driver);
>>> +
>>> +MODULE_AUTHOR("Karol Wrona <k.wrona@...sung.com>");
>>> +MODULE_DESCRIPTION("Samsung sensorhub accelerometers driver");
>>> +MODULE_LICENSE("GPL");
>>>
>>
>>
> 
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