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

[Benjamin Tissoires]

On Thu, Dec 18, 2014 at 12:26 PM, Peter Wu <peter@xxxxxxxxxxxxx> wrote:
> On Tuesday 16 December 2014 09:33:44 Benjamin Tissoires wrote:
>> Hi Peter,
>>
>> On Mon, Dec 15, 2014 at 7:50 PM, Peter Wu <peter@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
>> > ---
>>
>> 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
>
> Hi Benjamin,
>
> The Logitech Unifying extension for Chrome[1] is documented quite well
> and contains details which were not public before (including names and
> descriptions for all registers and subIDs!).
>
> In lib/devices/HidppFap.js you can find this logic for handling HID++
> 2.0 messages:
>
>     if ((reqView.getUint8(1) == rspView.getUint8(1)) //  device index
>         && (reqView.getUint8(2) == rspView.getUint8(2)) // feature index
>         && (reqView.getUint8(3) == rspView.getUint8(3))) // function/event ID + software ID
>     {
>         result.matchResult = devices.MATCH_RESULT.SUCCESS;
>     } else if ((reqView.getUint8(1) == rspView.getUint8(1)) //  device index
>         && (0xFF == rspView.getUint8(2)) // Hid++ 2.0 error
>         && (reqView.getUint8(2) == rspView.getUint8(3)) // feature index
>         && (reqView.getUint8(3) == rspView.getUint8(4))) // function/event ID + software ID
>     {
>         result.errCode = rspView.getUint8(5); // FAP_ERROR
>         result.matchResult = devices.MATCH_RESULT.ERROR;
>     }
>
> Looks like a sufficient proof that 0xFF is the correct number to detect
> HID++ 2.0 errors right?

Cool :)

Then the patch is:
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>

Cheers,
Benjamin


>
> In HID++ 1.0 devices ("rap"), 0xFF is named as "SYNC" (with no further
> comments), so this will probably not trigger false positives either.
>
> Kind regards,
> Peter
>
>  [1]: https://chrome.google.com/webstore/detail/logitech-unifying-for-chr/agpmgihmmmfkbhckmciedmhincdggomo
>
>> >  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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