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From: Johan Hovold <johan@kernel.org>
To: Johan Hovold <johan@kernel.org>
Cc: linux-usb@vger.kernel.org
Subject: [PATCH 02/11] USB: serial: mos7840: document MCS7810 detection hack
Date: Thu,  7 Nov 2019 14:28:55 +0100
Message-ID: <20191107132904.2379-3-johan@kernel.org> (raw)
In-Reply-To: <20191107132904.2379-1-johan@kernel.org>

Document the MCS7810 detection hack which relies on having the GPO and
GPI pins connected as recommended by ASIX.

Note that GPO (pin 42) is really RTS of the third port which will be
toggled for the corresponding physical port on two- and four-port
devices.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/mos7840.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index f13cf723fa6c..6de41a3c2dab 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -1955,6 +1955,13 @@ static int mos7840_ioctl(struct tty_struct *tty,
 	return -ENOIOCTLCMD;
 }
 
+/*
+ * Check if GPO (pin 42) is connected to GPI (pin 33) as recommended by ASIX
+ * for MCS7810 by bit-banging a 16-bit word.
+ *
+ * Note that GPO is really RTS of the third port so this will toggle RTS of
+ * port two or three on two- and four-port devices.
+ */
 static int mos7810_check(struct usb_serial *serial)
 {
 	int i, pass_count = 0;
-- 
2.23.0


  parent reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-07 13:28 [PATCH 00/11] USB: serial: mos7840: type detection and clean ups Johan Hovold
2019-11-07 13:28 ` [PATCH 01/11] USB: serial: mos7840: clean up device-type handling Johan Hovold
2019-11-07 13:28 ` Johan Hovold [this message]
2019-11-07 13:28 ` [PATCH 03/11] USB: serial: mos7840: fix probe error handling Johan Hovold
2019-11-07 13:28 ` [PATCH 04/11] USB: serial: mos7840: rip out broken interrupt handling Johan Hovold
2019-11-07 13:28 ` [PATCH 05/11] USB: serial: mos7840: drop redundant urb context check Johan Hovold
2019-11-07 13:28 ` [PATCH 06/11] USB: serial: mos7840: drop paranoid port checks Johan Hovold
2019-11-07 13:29 ` [PATCH 07/11] USB: serial: mos7840: drop paranoid serial checks Johan Hovold
2019-11-07 13:29 ` [PATCH 08/11] USB: serial: mos7840: drop serial struct accessor Johan Hovold
2019-11-07 13:29 ` [PATCH 09/11] USB: serial: mos7840: drop port driver data accessors Johan Hovold
2019-11-07 13:29 ` [PATCH 10/11] USB: serial: mos7840: drop read-urb check Johan Hovold
2019-11-07 13:29 ` [PATCH 11/11] USB: serial: mos7840: drop port open flag Johan Hovold
2019-11-11 13:27 ` [PATCH 00/11] USB: serial: mos7840: type detection and clean ups Greg KH
2019-11-12  9:21   ` Johan Hovold

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