[SRU][B/C/D/OEM-OSP1-B/E][PATCH 1/1] Input: alps - don't handle ALPS cs19 trackpoint-only device

[Andy Whitcroft]

On Tue, Jul 16, 2019 at 10:12:57PM +0800, Hui Wang wrote:
> BugLink: https://bugs.launchpad.net/bugs/1836752
> 
> On a latest Lenovo laptop, the trackpoint and 3 buttons below it
> don't work at all, when we move the trackpoint or press those 3
> buttons, the kernel will print out:
> "Rejected trackstick packet from non DualPoint device"
> 
> This device is identified as an alps touchpad but the packet has
> trackpoint format, so the alps.c drops the packet and prints out
> the message above.
> 
> According to XiaoXiao's explanation, this device is named cs19 and
> is trackpoint-only device, its firmware is only for trackpoint, it
> is independent of touchpad and is a device completely different from
> DualPoint ones.
> 
> To drive this device with mininal changes to the existing driver, we
> just let the alps driver not handle this device, then the trackpoint.c
> will be the driver of this device if the trackpoint driver is enabled.
> (if not, this device will fallback to a bare PS/2 device)
> 
> With the trackpoint.c, this trackpoint and 3 buttons all work well,
> they have all features that the trackpoint should have, like
> scrolling-screen, drag-and-drop and frame-selection.
> 
> Signed-off-by: XiaoXiao Liu <sliuuxiaonxiao at gmail.com>
> Signed-off-by: Hui Wang <hui.wang at canonical.com>
> Reviewed-by: Pali Rohár <pali.rohar at gmail.com>
> Cc: stable at vger.kernel.org
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov at gmail.com>
> (cherry picked from commit 7e4935ccc3236751e5fe4bd6846f86e46bb2e427
> git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git)
> Signed-off-by: Hui Wang <hui.wang at canonical.com>
> ---
>  drivers/input/mouse/alps.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
> index 0a6f7ca883e7..11a4363c3b60 100644
> --- a/drivers/input/mouse/alps.c
> +++ b/drivers/input/mouse/alps.c
> @@ -24,6 +24,7 @@
>  
>  #include "psmouse.h"
>  #include "alps.h"
> +#include "trackpoint.h"
>  
>  /*
>   * Definitions for ALPS version 3 and 4 command mode protocol
> @@ -2864,6 +2865,23 @@ static const struct alps_protocol_info *alps_match_table(unsigned char *e7,
>  	return NULL;
>  }
>  
> +static bool alps_is_cs19_trackpoint(struct psmouse *psmouse)
> +{
> +	u8 param[2] = { 0 };
> +
> +	if (ps2_command(&psmouse->ps2dev,
> +			param, MAKE_PS2_CMD(0, 2, TP_READ_ID)))
> +		return false;
> +
> +	/*
> +	 * param[0] contains the trackpoint device variant_id while
> +	 * param[1] contains the firmware_id. So far all alps
> +	 * trackpoint-only devices have their variant_ids equal

> +	 * TP_VARIANT_ALPS and their firmware_ids are in 0x20~0x2f range.
> +	 */
> +	return param[0] == TP_VARIANT_ALPS && (param[1] & 0x20);

I don't think the comment is consistent with the code.  I think the last
conditional should be something like the below to match the comment:

    ((param[1] | 0x0f) == 0x2f)

I have no idea if the comment is right, or the code is right.

> +}
> +
>  static int alps_identify(struct psmouse *psmouse, struct alps_data *priv)
>  {
>  	const struct alps_protocol_info *protocol;
> @@ -3164,6 +3182,20 @@ int alps_detect(struct psmouse *psmouse, bool set_properties)
>  	if (error)
>  		return error;
>  
> +	/*
> +	 * ALPS cs19 is a trackpoint-only device, and uses different
> +	 * protocol than DualPoint ones, so we return -EINVAL here and let
> +	 * trackpoint.c drive this device. If the trackpoint driver is not
> +	 * enabled, the device will fall back to a bare PS/2 mouse.
> +	 * If ps2_command() fails here, we depend on the immediately
> +	 * followed psmouse_reset() to reset the device to normal state.
> +	 */
> +	if (alps_is_cs19_trackpoint(psmouse)) {
> +		psmouse_dbg(psmouse,
> +			    "ALPS CS19 trackpoint-only device detected, ignoring\n");
> +		return -EINVAL;
> +	}
> +
>  	/*
>  	 * Reset the device to make sure it is fully operational:
>  	 * on some laptops, like certain Dell Latitudes, we may
> -- 
> 2.17.1
> 
> 
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