linux-kernel - Re: [PATCH 1/3] HID: logitech-hidpp: detect HID++ 2.0 errors too

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Message-ID: <CAN+gG=FiL1SY84W5acowe8hkoHnp6ObkbCtoeFu0s2juone=+Q@mail.gmail.com>
Date:	Tue, 16 Dec 2014 09:33:44 -0500
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Peter Wu <peter@...ensteyn.nl>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Nestor Lopez Casado <nlopezcasad@...itech.com>,
	linux-input <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] HID: logitech-hidpp: detect HID++ 2.0 errors too

Hi Peter,

On Mon, Dec 15, 2014 at 7:50 PM, Peter Wu <peter@...ensteyn.nl> wrote:
> Devices speaking HID++ 2.0 report a different error code (0xff). Detect
> these errors too to avoid 5 second delays when the device reports an
> error. Caught by... well, a bug in the QEMU emulation of this receiver.
>
> Renamed fap to rap for HID++ 1.0 errors because it is more logical,
> it has no functional difference.
>
> Signed-off-by: Peter Wu <peter@...ensteyn.nl>
> ---

I'd like to have Nestor's opinion on this. I did not manage to find on
the documentation that HID++ 2.0 Long report error code is 0xff, so
introducing this change without Logitech's blessing would be
unfortunate.
I understand this will fix your qemu problem, but I am not entirely
sure if we do not have to check on 0xff and 0x8f in both short and
long responses.

Cheers,
Benjamin

>  drivers/hid/hid-logitech-hidpp.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
> index 2f420c0..ae23dec 100644
> --- a/drivers/hid/hid-logitech-hidpp.c
> +++ b/drivers/hid/hid-logitech-hidpp.c
> @@ -105,6 +105,7 @@ struct hidpp_device {
>  };
>
>
> +/* HID++ 1.0 error codes */
>  #define HIDPP_ERROR                            0x8f
>  #define HIDPP_ERROR_SUCCESS                    0x00
>  #define HIDPP_ERROR_INVALID_SUBID              0x01
> @@ -119,6 +120,8 @@ struct hidpp_device {
>  #define HIDPP_ERROR_REQUEST_UNAVAILABLE                0x0a
>  #define HIDPP_ERROR_INVALID_PARAM_VALUE                0x0b
>  #define HIDPP_ERROR_WRONG_PIN_CODE             0x0c
> +/* HID++ 2.0 error codes */
> +#define HIDPP20_ERROR                          0xff
>
>  static void hidpp_connect_event(struct hidpp_device *hidpp_dev);
>
> @@ -192,9 +195,16 @@ static int hidpp_send_message_sync(struct hidpp_device *hidpp,
>         }
>
>         if (response->report_id == REPORT_ID_HIDPP_SHORT &&
> -           response->fap.feature_index == HIDPP_ERROR) {
> +           response->rap.sub_id == HIDPP_ERROR) {
> +               ret = response->rap.params[1];
> +               dbg_hid("%s:got hidpp error %02X\n", __func__, ret);
> +               goto exit;
> +       }
> +
> +       if (response->report_id == REPORT_ID_HIDPP_LONG &&
> +           response->fap.feature_index == HIDPP20_ERROR) {
>                 ret = response->fap.params[1];
> -               dbg_hid("__hidpp_send_report got hidpp error %02X\n", ret);
> +               dbg_hid("%s:got hidpp 2.0 error %02X\n", __func__, ret);
>                 goto exit;
>         }
>
> @@ -271,7 +281,8 @@ static inline bool hidpp_match_answer(struct hidpp_report *question,
>  static inline bool hidpp_match_error(struct hidpp_report *question,
>                 struct hidpp_report *answer)
>  {
> -       return (answer->fap.feature_index == HIDPP_ERROR) &&
> +       return ((answer->rap.sub_id == HIDPP_ERROR) ||
> +           (answer->fap.feature_index == HIDPP20_ERROR)) &&
>             (answer->fap.funcindex_clientid == question->fap.feature_index) &&
>             (answer->fap.params[0] == question->fap.funcindex_clientid);
>  }
> --
> 2.1.3
>
> --
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