From: Marc Zyngier <maz@kernel.org>
To: linux-usb@vger.kernel.org, linux-gpio@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: Linus Walleij <linus.walleij@linaro.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Johan Hovold <johan@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
kernel-team@android.com
Subject: [PATCH 0/4] USB: ftdio_sio: GPIO validity fixes
Date: Fri, 4 Dec 2020 16:47:35 +0000 [thread overview]
Message-ID: <20201204164739.781812-1-maz@kernel.org> (raw)
Having recently tried to use the CBUS GPIOs that come thanks to the
ftdio_sio driver, it occurred to me that the driver has a couple of
usability issues:
- it advertises potential GPIOs that are reserved to other uses (LED
control, or something else)
- it returns an odd error (-ENODEV), instead of the expected -EINVAL
when a line is unavailable, leading to a difficult diagnostic
We address the issues in a number of ways:
- Stop reporting invalid GPIO lines as valid to userspace. It
definitely seems odd to do so. Instead, report the line as being
used, making the userspace interface a bit more consistent.
- Implement the init_valid_mask() callback in the ftdi_sio driver,
allowing it to report which lines are actually valid.
- As suggested by Linus, give an indication to the user of why some of
the GPIO lines are unavailable, and point them to a useful tool
(once per boot). It is a bit sad that there next to no documentation
on how to use these CBUS pins.
- Drop the error reporting code, which has become useless at this
point.
Tested with a couple of FTDI devices (FT230X and FT231X) and various
CBUS configurations.
Marc Zyngier (4):
gpiolib: cdev: Flag invalid GPIOs as used
USB: serial: ftdi_sio: Report the valid GPIO lines to gpiolib
USB: serial: ftdi_sio: Log the CBUS GPIO validity
USB: serial: ftdi_sio: Drop GPIO line checking dead code
drivers/gpio/gpiolib-cdev.c | 1 +
drivers/usb/serial/ftdi_sio.c | 26 +++++++++++++++++++++++---
2 files changed, 24 insertions(+), 3 deletions(-)
--
2.28.0
next reply other threads:[~2020-12-04 16:48 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 16:47 Marc Zyngier [this message]
2020-12-04 16:47 ` [PATCH 1/4] gpiolib: cdev: Flag invalid GPIOs as used Marc Zyngier
2020-12-07 14:16 ` Johan Hovold
2020-12-07 14:59 ` Marc Zyngier
2020-12-09 9:25 ` Linus Walleij
2020-12-04 16:47 ` [PATCH 2/4] USB: serial: ftdi_sio: Report the valid GPIO lines to gpiolib Marc Zyngier
2020-12-09 9:28 ` Linus Walleij
2020-12-04 16:47 ` [PATCH 3/4] USB: serial: ftdi_sio: Log the CBUS GPIO validity Marc Zyngier
2020-12-07 14:29 ` Johan Hovold
2020-12-07 15:00 ` Marc Zyngier
2020-12-07 15:19 ` Johan Hovold
2020-12-09 9:35 ` Linus Walleij
2020-12-09 17:05 ` Johan Hovold
2020-12-09 17:39 ` Johan Hovold
2020-12-04 16:47 ` [PATCH 4/4] USB: serial: ftdi_sio: Drop GPIO line checking dead code Marc Zyngier
2020-12-07 9:55 ` [PATCH 0/4] USB: ftdio_sio: GPIO validity fixes Andy Shevchenko
2020-12-07 14:01 ` Johan Hovold
2020-12-07 14:41 ` Marc Zyngier
2020-12-07 15:08 ` Johan Hovold
2020-12-07 15:34 ` Marc Zyngier
2020-12-07 15:49 ` Johan Hovold
2020-12-09 9:20 ` Linus Walleij
2020-12-09 15:42 ` Johan Hovold
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