Re: [PATCH v3 3/4] HID: logitech: Add feature 0x0001: FeatureSet

[Mazin Rezk <mnrzk@protonmail.com>]

On Sunday, October 6, 2019 11:25 AM, Filipe Laíns <lains@archlinux.org> wrote:

> On Sun, 2019-10-06 at 01:04 +0000, Mazin Rezk wrote:
> > This patch adds support for the 0x0001 (FeatureSet) feature. This feature
> > is used to look up the feature ID of a feature index on a device and list
> > the total count of features on the device.
> >
> > I also added the hidpp20_get_features function which iterates through all
> > feature indexes on the device and stores a map of them in features an
> > hidpp_device struct. This function runs when an HID++ 2.0 device is probed.
> >
> > Signed-off-by: Mazin Rezk <mnrzk@protonmail.com>
> > ---
> >  drivers/hid/hid-logitech-hidpp.c | 92 ++++++++++++++++++++++++++++++++
> >  1 file changed, 92 insertions(+)
> >
> > diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
> > index a0efa8a43213..64ac94c581aa 100644
> > --- a/drivers/hid/hid-logitech-hidpp.c
> > +++ b/drivers/hid/hid-logitech-hidpp.c
> > @@ -190,6 +190,9 @@ struct hidpp_device {
> >
> >  	struct hidpp_battery battery;
> >  	struct hidpp_scroll_counter vertical_wheel_counter;
> > +
> > +	u16 *features;
> > +	u8 feature_count;
> >  };
> >
> >  /* HID++ 1.0 error codes */
> > @@ -911,6 +914,84 @@ static int hidpp_root_get_protocol_version(struct hidpp_device *hidpp)
> >  	return 0;
> >  }
> >
> > +/* -------------------------------------------------------------------------- */
> > +/* 0x0001: FeatureSet                                                         */
> > +/* -------------------------------------------------------------------------- */
> > +
> > +#define HIDPP_PAGE_FEATURESET				0x0001
> > +
> > +#define CMD_FEATURESET_GET_COUNT			0x00
> > +#define CMD_FEATURESET_GET_FEATURE			0x11
> > +
> > +static int hidpp20_featureset_get_feature(struct hidpp_device *hidpp,
>
> Can you change this to `hidpp20_featureset_get_feature_id` please? So
> that we keep in sync with the documentation, and to avoid minor
> confusion as IRoot has a `get_feature` function.

I will change this in v4, thanks.

>
> > +	u8 featureset_index, u8 feature_index, u16 *feature_id)
> > +{
> > +	struct hidpp_report response;
> > +	int ret;
> > +
> > +	ret = hidpp_send_fap_command_sync(hidpp, featureset_index,
> > +		CMD_FEATURESET_GET_FEATURE, &feature_index, 1, &response);
> > +
> > +	if (ret)
> > +		return ret;
> > +
> > +	*feature_id = (response.fap.params[0] << 8) | response.fap.params[1];
> > +
> > +	return ret;
> > +}
> > +
> > +static int hidpp20_featureset_get_count(struct hidpp_device *hidpp,
> > +	u8 feature_index, u8 *count)
> > +{
> > +	struct hidpp_report response;
> > +	int ret;
> > +
> > +	ret = hidpp_send_fap_command_sync(hidpp, feature_index,
> > +		CMD_FEATURESET_GET_COUNT, NULL, 0, &response);
> > +
> > +	if (ret)
> > +		return ret;
> > +
> > +	*count = response.fap.params[0];
> > +
> > +	return ret;
> > +}
>
> Just a nitpick but can we put this before
> `hidpp20_featureset_get_feature`? This way we keep the ID order.

That makes sense. I will change this in v4, thanks.

>
> > +
> > +static int hidpp20_get_features(struct hidpp_device *hidpp)
> > +{
> > +	int ret;
> > +	u8 featureset_index, featureset_type;
> > +	u8 i;
> > +
> > +	hidpp->feature_count = 0;
> > +
> > +	ret = hidpp_root_get_feature(hidpp, HIDPP_PAGE_FEATURESET,
> > +				     &featureset_index, &featureset_type);
> > +
> > +	if (ret == -ENOENT) {
> > +		hid_warn(hidpp->hid_dev, "Unable to retrieve feature set.");
> > +		return 0;
> > +	}
> > +
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = hidpp20_featureset_get_count(hidpp, featureset_index,
> > +		&hidpp->feature_count);
> > +
> > +	if (ret)
> > +		return ret;
> > +
> > +	hidpp->features = devm_kzalloc(&hidpp->hid_dev->dev,
> > +			hidpp->feature_count * sizeof(u16), GFP_KERNEL);
> > +
> > +	for (i = 0; i < hidpp->feature_count && !ret; i++)
> > +		ret = hidpp20_featureset_get_feature(hidpp, featureset_index,
> > +				i, &(hidpp->features[i]));
> > +
> > +	return ret;
> > +}
> > +
> >  /* -------------------------------------------------------------------------- */
> >  /* 0x0005: GetDeviceNameType                                                  */
> >  /* -------------------------------------------------------------------------- */
>
> Please use `DeviceNameType` here to keep in sync with the
> documentation.

Since I have not modified GetDeviceNameType in this patch, I will keep it
the way it was for now. This could probably be changed in a different and
unrelated patch.

>
> > @@ -3625,6 +3706,17 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
> >  		hidpp_overwrite_name(hdev);
> >  	}
> >
> > +	/* Cache feature indexes and IDs to check reports faster */
> > +	if (hidpp->protocol_major >= 2) {
> > +		if (hidpp20_get_features(hidpp)) {
> > +			hid_err(hdev, "%s:hidpp20_get_features returned error\n",
> > +				__func__);
> > +			goto hid_hw_init_fail;
> > +		}
> > +	} else {
> > +		hidpp->feature_count = 0;
> > +	}
>
> I have not looked at the whole code that much but is the else really
> needed here?

I wanted to initialize feature_count to 0 if the device was either
HID++ 1.0 or did not support FeatureSet. This was so that, just in case
its features array was accessed, it would not try to check an uninitialized
array. Although, I could probably remove the else statement and set
feature_count to 0 before the if statement. I would also be able to remove
the redundant initialization statement in hidpp20_get_features.

I will make these changes in v4, thanks.

>
> > +
> >  	if (connected && (hidpp->quirks & HIDPP_QUIRK_CLASS_WTP)) {
> >  		ret = wtp_get_config(hidpp);
> >  		if (ret)
> > --
> > 2.23.0
> >
> --
> Filipe Laíns
> 3DCE 51D6 0930 EBA4 7858 BA41 46F6 33CB B0EB 4BF2