Re: [PATCH v4 RESEND] hid-ft260: Add serial driver

[Michael Zaidman <michael.zaidman@gmail.com>]

On Thu, Dec 28, 2023 at 12:50:08PM +0100, Christina Quast wrote:
> Hi everyone!
> 
> On 12/18/23 10:31, Christina Quast wrote:
> > Adds the serial driver for FT260 USB HID devices, providing direct and
> > simplified access to UART functionality without the need for FT260 HID
> > report format knowledge.
> > 
> > This chip implements an UART and I2C interface, but only the latter was
> > previously supported with a kernel driver. For the UART interface, only
> > FTDI example code using hidraw from userspace was available.
> > 
> > This commit adds a serial interface /dev/ttyFTx (FT as in FT260), which
> > implements tty serial driver ops, facilitating baudrate configuration,
> > data transmission and reception, termios settings.
> > 
> > Signed-off-by: Daniel Beer <daniel.beer@igorinstitute.com>
> > Signed-off-by: Christina Quast <contact@christina-quast.de>
> > Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Reviewed-by: David Lamparter <equinox@diac24.net>
> 
> Is this already queued for 6.8?
> 
> Cheers and happy new year!
> 
> Christina
> 

Thanks for this work!

I am adding Jiri Kosina, the maintainer of the HID subsystem.

The FTDI FT260 chip implements three functionalities: USB to I2C, UART,
and GPIO bridges through two USB HID class interfaces.

I use the https://github.com/MichaelZaidman/hid-ft260 repository for FT260
driver development. The I2C support has been upstreamed since 5.13. The code
is mature enough and is I2C performance-tuned.

The initial GPIO support was developed and committed into the mainline
https://patchwork.kernel.org/project/linux-input/cover/20230211115752.26276-1-michael.zaidman@gmail.com/.

Two versions of the initial UART support were around for some time, and
now they are unified in this commit.

I am going to test it with I2C traffic to exclude a suspect of possible
impact on the I2C performance and will provide feedback in a week or two.

--Michael

> > ---
> > 
> > V1 -> V2: Adressed review comments, added power saving mode quirk
> > V2 -> V3: Added return 0 in ft260_i2c_probe function
> > V3 -> V4:
> >   - Adressed review comments
> >   - Added get_icount
> >   - Fixed tty port lifetime bug
> > 
> >   drivers/hid/hid-ft260.c | 833 +++++++++++++++++++++++++++++++++++++---
> >   1 file changed, 781 insertions(+), 52 deletions(-)