linux-kernel - Re: [PATCH] HID: i2c-hid: support sending HID output reports using the output register

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Date:	Fri, 14 Jun 2013 18:35:32 +0200
From:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:	Andrew Duggan <aduggan@...aptics.com>
CC:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jiri Kosina <jkosina@...e.cz>
Subject: Re: [PATCH] HID: i2c-hid: support sending HID output reports using
 the output register

Hi Andrew,

On 06/14/2013 12:54 AM, Andrew Duggan wrote:
> The current i2c hid driver does not support sending HID output reports using
> the output register for devices which support receiving reports through this
> method. This patch determines which method to use to send output reports based
>  on the value of wMaxOutputLength in the device's HID descriptor.
> 
> Signed-off-by: Andrew Duggan <aduggan@...aptics.com>

I have very few comments (actually we already discussed this off-list).

I'm just nitpicking, so I think I can give my:
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>

Jiri, you can decide whether it worth a v2 or not (I'm fine with the
current code):

> ---
>  drivers/hid/i2c-hid/i2c-hid.c |   18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
> index 2b1799a..a71c9a7 100644
> --- a/drivers/hid/i2c-hid/i2c-hid.c
> +++ b/drivers/hid/i2c-hid/i2c-hid.c
> @@ -108,6 +108,7 @@ static const struct i2c_hid_cmd hid_reset_cmd =		{ I2C_HID_CMD(0x01),
>  static const struct i2c_hid_cmd hid_get_report_cmd =	{ I2C_HID_CMD(0x02) };
>  static const struct i2c_hid_cmd hid_set_report_cmd =	{ I2C_HID_CMD(0x03) };
>  static const struct i2c_hid_cmd hid_set_power_cmd =	{ I2C_HID_CMD(0x08) };
> +static const struct i2c_hid_cmd hid_no_cmd =		{ .length = 0 };
>  
>  /*
>   * These definitions are not used here, but are defined by the spec.
> @@ -259,8 +260,11 @@ static int i2c_hid_set_report(struct i2c_client *client, u8 reportType,
>  {
>  	struct i2c_hid *ihid = i2c_get_clientdata(client);
>  	u8 *args = ihid->argsbuf;
> +	struct i2c_hid_cmd hidcmd = hid_set_report_cmd;

We can use a pointer here instead of an allocated structure (as
hid_set_report_cmd is a const).

>  	int ret;
>  	u16 dataRegister = le16_to_cpu(ihid->hdesc.wDataRegister);
> +	u16 outputRegister = le16_to_cpu(ihid->hdesc.wOutputRegister);
> +	u16 maxOutputLength = le16_to_cpu(ihid->hdesc.wMaxOutputLength);
>  
>  	/* hidraw already checked that data_len < HID_MAX_BUFFER_SIZE */
>  	u16 size =	2			/* size */ +
> @@ -278,8 +282,16 @@ static int i2c_hid_set_report(struct i2c_client *client, u8 reportType,
>  		reportID = 0x0F;
>  	}
>  
> -	args[index++] = dataRegister & 0xFF;
> -	args[index++] = dataRegister >> 8;
> +	/* use the data register for feature reports or if the device does not
> +	 * support the output register */

This comment does not follow the multi lines comments guideline. It
should be:
/*
 * use the data register for feature reports or if the device does not
 * support the output register
 */

So, just few not very important things. Sorry for not spotting this earlier.

Cheers,
Benjamin

> +	if (reportType == 0x03 || maxOutputLength == 0) {
> +		args[index++] = dataRegister & 0xFF;
> +		args[index++] = dataRegister >> 8;
> +	} else {
> +		args[index++] = outputRegister & 0xFF;
> +		args[index++] = outputRegister >> 8;
> +		hidcmd = hid_no_cmd;
> +	}
>  
>  	args[index++] = size & 0xFF;
>  	args[index++] = size >> 8;
> @@ -289,7 +301,7 @@ static int i2c_hid_set_report(struct i2c_client *client, u8 reportType,
>  
>  	memcpy(&args[index], buf, data_len);
>  
> -	ret = __i2c_hid_command(client, &hid_set_report_cmd, reportID,
> +	ret = __i2c_hid_command(client, &hidcmd, reportID,
>  		reportType, args, args_len, NULL, 0);
>  	if (ret) {
>  		dev_err(&client->dev, "failed to set a report to device.\n");
> 

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