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[152.23.88.220]) by smtp.gmail.com with ESMTPSA id u19sm9741710qtw.14.2021.11.07.12.02.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 07 Nov 2021 12:02:27 -0800 (PST) Message-ID: <3a98b10e-6b78-b769-e22d-2496d7bcd69d@cs.unc.edu> Date: Sun, 7 Nov 2021 15:02:27 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH] Input: elantench - Fix the firmware misreport coordinates for trackpoint occasionally. Content-Language: en-US To: Dmitry Torokhov Cc: linux-kernel@vger.kernel.org, linux-input@vger.kernel.org, jingle.wu@emc.com.tw, josh.chen@emc.com.tw, dave.wang@emc.com.tw, phoenix References: <20210729010940.5752-1-phoenix@emc.com.tw> <000001d79d99$53762dd0$fa628970$@emc.com.tw> From: Yufei Du In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org Hi Dmitry, I am a user currently suffering from the firmware bug that causes my trackpoint to be unusable on my Lenovo X13 Gen 1 AMD. I tested this patch in the latest 5.15 mainline kernel tree and can possibly answer your questions regarding the patch. > I think this will reject X coordinates in range [0, 127]. Is this really > what is needed? As Phoenix explained in his reply, the patch will reject X and Y coordinates larger than 127 or smaller than -127. This is because the most significant bit of packet[1] (for X) and packet[2] (for Y) are inverse of the sign bit. Although I do not have the formal design specification of the device, I tried pushing the trackpoint as hard as I could, and the X and Y coordinates never go beyond +/-127 normally, so I believe that this patch would not cause any functionality issue. > What kind of patterns are you observing when firmware > misreports coordinates? Here is a sample log I observed (with elantech.debug set to 2 for more debugging messages): psmouse serio1: elantech: PS/2 packet [10 00 80 26 f9 0a] psmouse serio1: elantech: PS/2 packet [10 00 80 26 00 80] psmouse serio1: elantech: PS/2 packet [10 00 80 00 00 00] psmouse serio1: Touchpad at isa0060/serio1/input0 lost sync at byte 6 psmouse serio1: elantech: PS/2 packet [10 00 80 26 f8 0b] psmouse serio1: Touchpad at isa0060/serio1/input0 - driver resynced. The first packet is a valid packet. The second packet is the incorrect packet that this patch prevents. The third packet is a corrupted packet that psmouse detects (as shown in the "lost sync" message), and the fourth packet is a valid packet again. Without the patch, the second packet would cause the cursor to jump to the edge of the screen. So far, all my logs of this issue show the same pattern of a jumpy incorrect packet followed by a corrupted packet that causes psmouse to lose sync. There are more logs and discussions in the BugZilla entry here: https://bugzilla.kernel.org/show_bug.cgi?id=209167 Hope my explanation helped a bit. Thanks! Best, Yufei Du