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

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Message-ID: <e0dc8d111e1615d35da0c87b4b93b55b3bb89f23.camel@archlinux.org>
Date:   Sun, 06 Oct 2019 16:25:20 +0100
From:   Filipe Laíns <lains@...hlinux.org>
To:     Mazin Rezk <mnrzk@...tonmail.com>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>
Cc:     "benjamin.tissoires@...hat.com" <benjamin.tissoires@...hat.com>,
        "jikos@...nel.org" <jikos@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] HID: logitech: Add feature 0x0001: FeatureSet

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@...tonmail.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.

> +	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.

> +
> +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.

> @@ -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?

> +
>  	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

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