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[174.94.156.236]) by smtp.googlemail.com with ESMTPSA id c186-20020ae9edc3000000b006a37eb728cfsm67195qkg.1.2022.05.24.12.27.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 May 2022 12:27:23 -0700 (PDT) From: Guillaume Champagne To: champagne.guillaume.c@gmail.com, michael.zaidman@gmail.com, jikos@kernel.org, benjamin.tissoires@redhat.com Cc: linux-i2c@vger.kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Mathieu Gallichand Subject: [PATCH] HID: ft260: fix multi packet i2c transactions Date: Tue, 24 May 2022 15:24:22 -0400 Message-Id: <20220524192422.13967-1-champagne.guillaume.c@gmail.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org Only trigger START and STOP conditions for the first and last HID packets when i2c writes are split in multiple packets. Otherwise, slave i2c devices receive each packet as standalone i2c transactions. Since i2c slave devices clear their internal state on STOP, this breaks auto increment of the register address written to. Concretely, SCL is now held low between processing of HID packets so i2c slave devices know to keep increment the same register address when the next bytes arrive. Co-developed-by: Mathieu Gallichand Signed-off-by: Mathieu Gallichand Signed-off-by: Guillaume Champagne --- drivers/hid/hid-ft260.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c index 79505c64dbfe..9c5912a21ccb 100644 --- a/drivers/hid/hid-ft260.c +++ b/drivers/hid/hid-ft260.c @@ -390,6 +390,8 @@ static int ft260_i2c_write(struct ft260_device *dev, u8 addr, u8 *data, struct hid_device *hdev = dev->hdev; struct ft260_i2c_write_request_report *rep = (struct ft260_i2c_write_request_report *)dev->write_buf; + bool multi_packet = data_len > FT260_WR_DATA_MAX; + u8 packet_flag = multi_packet ? flag & FT260_FLAG_START_REPEATED : flag; do { if (data_len <= FT260_WR_DATA_MAX) @@ -400,7 +402,7 @@ static int ft260_i2c_write(struct ft260_device *dev, u8 addr, u8 *data, rep->report = FT260_I2C_DATA_REPORT_ID(len); rep->address = addr; rep->length = len; - rep->flag = flag; + rep->flag = packet_flag; memcpy(rep->data, &data[idx], len); @@ -418,6 +420,12 @@ static int ft260_i2c_write(struct ft260_device *dev, u8 addr, u8 *data, data_len -= len; idx += len; + if (multi_packet) { + if (data_len <= FT260_WR_DATA_MAX) + packet_flag = flag & FT260_FLAG_STOP; + else + packet_flag = FT260_FLAG_NONE; + } } while (data_len > 0); return 0;