Re: [patch v6 0/3] JTAG driver introduction

[Rick Altherr]

On Fri, Aug 25, 2017 at 1:50 AM, Stuart Longland
<stuartl@xxxxxxxxxxxxxxxxxx> wrote:
> [Note: dropping vadimp@xxxxxxxxxxxxx as SMTP server complained about the
> DNS server returning NXDOMAIN.  Apologies.]
> On 25/08/17 18:32, Linus Walleij wrote:
>> Gnah!
>> Whoever writes a slot-in replacement making the character device
>> take precendence wins lots of karma.
>
> What would such a replacement look like though?

See Linus's comments about using the existing kernel GPIO chardev
interface.  It already supports requesting multiple GPIO line state
changes in a single request.

>
> Some sort of system whereby you can read/write single-line commands as
> if talking to a GPIO expander over a UART?
>
> Would you access the GPIOs one by one, or would you perhaps map them
> into a bitmap (maybe arbitrarily, up to 64-bits wide) and perform masked
> operations on the bitmap?
>
> I'm no fan of the sysfs GPIO interface, but it beats poking around at
> registers behind the kernel's back.
> --
> Stuart Longland (aka Redhatter, VK4MSL)
>
> I haven't lost my mind...
>   ...it's backed up on a tape somewhere.
>