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Date:   Tue, 21 May 2019 11:46:22 +0200
From:   Pali =?utf-8?B?Um9ow6Fy?= <pali.rohar@gmail.com>
To:     Hui Wang <hui.wang@canonical.com>
Cc:     Xiaoxiao Liu <xiaoxiao.liu-1@cn.alps.com>,
        XiaoXiao Liu <sliuuxiaonxiao@gmail.com>,
        "dmitry.torokhov@gmail.com" <dmitry.torokhov@gmail.com>,
        "linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Xiaojian Cao <xiaojian.cao@cn.alps.com>,
        "zhangfp1@lenovo.com" <zhangfp1@lenovo.com>
Subject: Re: =?utf-8?B?562U5aSNOiBbUEFUQ0hdIGlucHV0?= =?utf-8?Q?=3A?=
 alps-fix the issue the special alps trackpoint do not work.
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Hello!

On Tuesday 21 May 2019 10:26:47 Hui Wang wrote:
> Tested-by: Hui Wang <hui.wang@canonical.com>
> 
> On 2019/5/21 上午9:07, Xiaoxiao Liu wrote:
> > Add Pali Rohár.
> > 
> > -----邮件原件-----
> > 发件人: XiaoXiao Liu <sliuuxiaonxiao@gmail.com>
> > 发送时间: Monday, May 20, 2019 7:02 PM
> > 收件人: dmitry.torokhov@gmail.com
> > 抄送: linux-input@vger.kernel.org; linux-kernel@vger.kernel.org; hui.wang@canonical.com; 曹 曉建 Xiaojian Cao <xiaojian.cao@cn.alps.com>; zhangfp1@lenovo.com; 劉 曉曉 Xiaoxiao Liu <xiaoxiao.liu-1@cn.alps.com>; XiaoXiao Liu <sliuuxiaonxiao@gmail.com>
> > 主题: [PATCH] input: alps-fix the issue the special alps trackpoint do not work.
> > 
> > when the alps trackpoint is detected and using the alps_v8_protocol_data procotol,
> > the alps driver will not report the input data.

Why it does not report input data?

> > solution: use standard mouse driver instead of alps driver when the specail trackpoint was detected.

This looks like an (undocumented) hack or workaround. Not a solution.

> > Signed-off-by: XiaoXiao Liu <sliuuxiaonxiao@gmail.com>
> > ---
> >   drivers/input/mouse/alps.c | 23 ++++++++++++++++++++++-
> >   1 file changed, 22 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c index 0a6f7ca883e7..516ae1d0eb17 100644
> > --- a/drivers/input/mouse/alps.c
> > +++ b/drivers/input/mouse/alps.c
> > @@ -24,7 +24,7 @@
> >   #include "psmouse.h"
> >   #include "alps.h"
> > -
> > +#include "trackpoint.h"
> >   /*
> >    * Definitions for ALPS version 3 and 4 command mode protocol
> >    */
> > @@ -2864,6 +2864,22 @@ static const struct alps_protocol_info *alps_match_table(unsigned char *e7,
> >   	return NULL;
> >   }
> > +int alps_check_is_trackpoint(struct psmouse *psmouse) {
> > +	u8 param[2] = { 0 };
> > +	int error;
> > +
> > +	error = ps2_command(&psmouse->ps2dev,
> > +			    param, MAKE_PS2_CMD(0, 2, TP_READ_ID));
> > +	if (error)
> > +		return error;
> > +
> > +	if (param[0] == TP_VARIANT_ALPS)
> > +		return 0;
> > +	psmouse_warn(psmouse, "It is not alps trackpoint.\n");
> > +	return -ENODEV;
> > +}

So, this function returns 0 when detected ALPS trackpoint and -ENODEV
when not.

> > +
> >   static int alps_identify(struct psmouse *psmouse, struct alps_data *priv)  {
> >   	const struct alps_protocol_info *protocol; @@ -2912,6 +2928,11 @@ static int alps_identify(struct psmouse *psmouse, struct alps_data *priv)
> >   			protocol = &alps_v3_protocol_data;
> >   		} else if (e7[0] == 0x73 && e7[1] == 0x03 &&
> >   			   (e7[2] == 0x14 || e7[2] == 0x28)) {
> > +				if (alps_check_is_trackpoint(psmouse) == 0) {
> > +					psmouse_warn(psmouse,
> > +					"It is alps trackpoint, use the standard mouse driver.\n");
> > +					return -EINVAL;

And here I'm lost. If we have *not* detected ALPS trackpoint then if
block is not called which means that ALPS driver is used.

So why is for non-ALPS trackpoints used ALPS driver? This does not seem
like a correct...

And when we have detected ALPS trackpoint (return value 0) then standard
mouse driver is used and returned -EINVAL. This seems strange too.

So either this code is wrong or there are missing more details for
explaining this strange logic. But still this looks like a hack not a
proper fix/solution.

> > +				}
> >   			protocol = &alps_v8_protocol_data;
> >   		} else if (e7[0] == 0x73 && e7[1] == 0x03 && e7[2] == 0xc8) {
> >   			protocol = &alps_v9_protocol_data;
> > --
> > 2.20.1
> > 

-- 
Pali Rohár
pali.rohar@gmail.com