On Fri, Dec 4, 2020 at 6:49 PM Marc Zyngier <maz@xxxxxxxxxx> 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@xxxxxxxxx> > 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
