Re: [PATCH 0/4] USB: ftdio_sio: GPIO validity fixes

[Andy Shevchenko <andy.shevchenko@gmail.com>]

On Fri, Dec 4, 2020 at 6:49 PM Marc Zyngier <maz@kernel.org> wrote:
>
> 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.

Series looks pretty good to me, FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

> 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
>


-- 
With Best Regards,
Andy Shevchenko