Re: [PATCH v3 2/3] Input: adc-joystick - Add polled input device support

Artur Rojek
2022-06-18T13:08:56Z

On 2022-06-15 17:12, Chris Morgan wrote:
> On Wed, Jun 15, 2022 at 03:43:07AM +0200, Artur Rojek wrote:
>> On 2022-06-13 21:23, Chris Morgan wrote:
>> > From: Chris Morgan <macromorgan@hotmail.com>
>> >
>> > Add polled input device support to the adc-joystick driver. This is
>> > useful for devices which do not have hardware capable triggers on
>> > their SARADC. Code modified from adc-joystick.c changes made by Maya
>> > Matuszczyk.
>> >
>> > Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
>> > Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
>>
>> Hi Chris,
>>
>> Comments inline. I also Cc'd Paul and Jonathan, who were attached in
>> v2.
>>
>> > ---
>> > drivers/input/joystick/adc-joystick.c | 52 +++++++++++++++++++++------
>> > 1 file changed, 41 insertions(+), 11 deletions(-)
>> >
>> > diff --git a/drivers/input/joystick/adc-joystick.c
>> > b/drivers/input/joystick/adc-joystick.c
>> > index 78ebca7d400a..dc01cd0214d2 100644
>> > --- a/drivers/input/joystick/adc-joystick.c
>> > +++ b/drivers/input/joystick/adc-joystick.c
>> > @@ -13,6 +13,10 @@
>> >
>> > #include <asm/unaligned.h>
>> >
>> > +#define ADC_JSK_POLL_INTERVAL 16
>> > +#define ADC_JSK_POLL_MIN 8
>> > +#define ADC_JSK_POLL_MAX 32
>> > +
>> > struct adc_joystick_axis {
>> > u32 code;
>> > s32 range[2];
>> > @@ -26,8 +30,21 @@ struct adc_joystick {
>> > struct adc_joystick_axis *axes;
>> > struct iio_channel *chans;
>> > int num_chans;
>> > + bool polled;
>> > };
>> >
>> > +static void adc_joystick_poll(struct input_dev *input)
>> > +{
>> > + struct adc_joystick *joy = input_get_drvdata(input);
>> > + int i, val;
>> > +
>> > + for (i = 0; i < joy->num_chans; i++) {
>> > + iio_read_channel_raw(&joy->chans[i], &val);
>> > + input_report_abs(input, joy->axes[i].code, val);
>> > + }
>> > + input_sync(input);
>> > +}
>> > +
>> > static int adc_joystick_handle(const void *data, void *private)
>> > {
>> > struct adc_joystick *joy = private;
>> > @@ -215,8 +232,19 @@ static int adc_joystick_probe(struct
>> > platform_device *pdev)
>> > joy->input = input;
>> > input->name = pdev->name;
>> > input->id.bustype = BUS_HOST;
>> > - input->open = adc_joystick_open;
>> > - input->close = adc_joystick_close;
>> > +
>> > + if (device_property_read_bool(dev,
>> > "adc-joystick,no-hardware-trigger"))
>> > + joy->polled = 1;
>> As mentioned in v2, I don't think a DT property is required here.
>> Assuming
>> the polled mode is a fallback for devices with no buffers, just do:
>> ```
>> joy->polled = !(joy->chans[0].indio_dev->modes &
>> INDIO_ALL_BUFFER_MODES);
>> ```
>
> Understood. I attempted this and noticed that it was showing I have
> INDIO_BUFFER_TRIGGERED in addition to INDIO_DIRECT_MODE (the
> INDIO_DIRECT_MODE is the only one specified at the hardware level
> though). Should I just check for INDIO_BUFFER_SOFTWARE &
> INDIO_BUFFER_HARDWARE instead? I think it's possible that the inclusion
> of the industrialio_triggered_buffer module in my kernel is adding
> this to the channel somehow?
Having INDIO_BUFFER_TRIGGERED means that your saradc is capable of using
the existing flow. You should be able to register a software trigger and
use the adc-joystick driver without further issues.
That said, this is where it gets problematic - there is no way to create
an IIO trigger via Device Tree, since triggers don't describe any piece
of hardware, and you shouldn't need to register it at runtime
(configfs/sysfs) for communication between two kernel drivers either. At
the same time, it's not adc-joystick's job to register an external
trigger.

Jonathan,
I don't know what the proper approach to this should be, perhaps you
could assist?

Cheers,
Artur
>
> Thank you.
>
>> > +
>> > + if (joy->polled) {
>> > + input_setup_polling(input, adc_joystick_poll);
>> > + input_set_poll_interval(input, ADC_JSK_POLL_INTERVAL);
>> > + input_set_min_poll_interval(input, ADC_JSK_POLL_MIN);
>> > + input_set_max_poll_interval(input, ADC_JSK_POLL_MAX);
>> > + } else {
>> > + input->open = adc_joystick_open;
>> > + input->close = adc_joystick_close;
>> > + }
>> >
>> > error = adc_joystick_set_axes(dev, joy);
>> > if (error)
>> > @@ -229,16 +257,18 @@ static int adc_joystick_probe(struct
>> > platform_device *pdev)
>> > return error;
>> > }
>> >
>> > - joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle, joy);
>> > - if (IS_ERR(joy->buffer)) {
>> > - dev_err(dev, "Unable to allocate callback buffer\n");
>> > - return PTR_ERR(joy->buffer);
>> > - }
>> > + if (!joy->polled) {
>> > + joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle, joy);
>> Please maintain line discipline of 80 chars to stay consistent with
>> the rest
>> of this driver.
>
> Understood, sorry about that.
>
>> > + if (IS_ERR(joy->buffer)) {
>> > + dev_err(dev, "Unable to allocate callback buffer\n");
>> > + return PTR_ERR(joy->buffer);
>> > + }
>> >
>> > - error = devm_add_action_or_reset(dev, adc_joystick_cleanup,
>> > joy->buffer);
>> > - if (error) {
>> > - dev_err(dev, "Unable to add action\n");
>> > - return error;
>> > + error = devm_add_action_or_reset(dev, adc_joystick_cleanup,
>> > joy->buffer);
>> Same here.
>
> Ditto.
>
>>
>> Cheers,
>> Artur
>> > + if (error) {
>> > + dev_err(dev, "Unable to add action\n");
>> > + return error;
>> > + }
>> > }
>> >
>> > return 0;