linux-kernel - Re: [PATCH v2] Input: elantech: Enable SMBus on new (2018+) systems

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Date:   Mon, 21 Jan 2019 09:33:14 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        廖崇榮 <kt.liao@....com.tw>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] Input: elantech: Enable SMBus on new (2018+) systems

On Mon, Jan 21, 2019 at 8:03 AM Kai-Heng Feng
<kai.heng.feng@...onical.com> wrote:
>
> There are some new HP laptops with Elantech touchpad don't support
> multitouch.
>
> Currently we use ETP_NEW_IC_SMBUS_HOST_NOTIFY() to check if SMBus is
> supported, but in addition to firmware version, the bus type also
> informs us if the IC can support SMBus, so also check that.
>
> In case of breaking old ICs, only enables SMBus on systems manufactured
> after 2018, alongsides aforementioned checks.
>
> Lastly, consolidats all check into elantech_use_host_notify() and use it
> to determine whether to use PS/2 or SMBus.
>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
> v2:
> - Wording.
> - Further restrain on older systems (< 2018).
>
>  drivers/input/mouse/elantech.c | 63 ++++++++++++++++++----------------
>  1 file changed, 34 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
> index 9fe075c137dc..2594130b0079 100644
> --- a/drivers/input/mouse/elantech.c
> +++ b/drivers/input/mouse/elantech.c
> @@ -1799,6 +1799,39 @@ static int elantech_create_smbus(struct psmouse *psmouse,
>                                   leave_breadcrumbs);
>  }
>
> +static bool elantech_use_host_notify(struct psmouse *psmouse,
> +                                    struct elantech_device_info *info)
> +{
> +       bool host_notify = false;
> +
> +       if (ETP_NEW_IC_SMBUS_HOST_NOTIFY(info->fw_version))
> +               host_notify = true;
> +       else {
> +               switch (info->bus) {
> +               case ETP_BUS_PS2_ONLY:
> +                       /* expected case */
> +                       break;
> +               case ETP_BUS_SMB_ALERT_ONLY:
> +                       /* fall-through  */
> +               case ETP_BUS_PS2_SMB_ALERT:
> +                       psmouse_dbg(psmouse, "Ignoring SMBus provider through alert protocol.\n");
> +                       break;
> +               case ETP_BUS_SMB_HST_NTFY_ONLY:
> +                       /* fall-through  */
> +               case ETP_BUS_PS2_SMB_HST_NTFY:
> +                       host_notify = true;
> +                       break;
> +               default:
> +                       psmouse_dbg(psmouse,
> +                                   "Ignoring SMBus bus provider %d.\n",
> +                                   info->bus);
> +               }
> +       }
> +
> +       /* SMbus implementation is stable after 2018 */
> +       return host_notify && (dmi_get_bios_year() >= 2018);

Strictly speaking, the check for the year should be in the `switch
(info->bus)`, but OTOH, laptops with ETP_NEW_IC_SMBUS_HOST_NOTIFY
should be manufactured after 2018 too, so we should be good.

Acked-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>

Cheers,
Benjamin

> +}
> +
>  /**
>   * elantech_setup_smbus - called once the PS/2 devices are enumerated
>   * and decides to instantiate a SMBus InterTouch device.
> @@ -1818,7 +1851,7 @@ static int elantech_setup_smbus(struct psmouse *psmouse,
>                  * i2c_blacklist_pnp_ids.
>                  * Old ICs are up to the user to decide.
>                  */
> -               if (!ETP_NEW_IC_SMBUS_HOST_NOTIFY(info->fw_version) ||
> +               if (!elantech_use_host_notify(psmouse, info) ||
>                     psmouse_matches_pnp_id(psmouse, i2c_blacklist_pnp_ids))
>                         return -ENXIO;
>         }
> @@ -1838,34 +1871,6 @@ static int elantech_setup_smbus(struct psmouse *psmouse,
>         return 0;
>  }
>
> -static bool elantech_use_host_notify(struct psmouse *psmouse,
> -                                    struct elantech_device_info *info)
> -{
> -       if (ETP_NEW_IC_SMBUS_HOST_NOTIFY(info->fw_version))
> -               return true;
> -
> -       switch (info->bus) {
> -       case ETP_BUS_PS2_ONLY:
> -               /* expected case */
> -               break;
> -       case ETP_BUS_SMB_ALERT_ONLY:
> -               /* fall-through  */
> -       case ETP_BUS_PS2_SMB_ALERT:
> -               psmouse_dbg(psmouse, "Ignoring SMBus provider through alert protocol.\n");
> -               break;
> -       case ETP_BUS_SMB_HST_NTFY_ONLY:
> -               /* fall-through  */
> -       case ETP_BUS_PS2_SMB_HST_NTFY:
> -               return true;
> -       default:
> -               psmouse_dbg(psmouse,
> -                           "Ignoring SMBus bus provider %d.\n",
> -                           info->bus);
> -       }
> -
> -       return false;
> -}
> -
>  int elantech_init_smbus(struct psmouse *psmouse)
>  {
>         struct elantech_device_info info;
> --
> 2.17.1
>