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

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On Tue, Aug 22, 2017 at 6:10 PM, Oleksandr Shamray
<oleksandrs@mellanox.com> wrote:

> SoC which are not equipped with JTAG master interface, can be built
> on top of JTAG core driver infrastructure, by applying bit-banging of
> TDI, TDO, TCK and TMS pins within the hardware specific driver.

I guess you mean it should then use GPIO lines for bit-banging?

I was wondering about how some JTAG clients like openOCD does
this in some cases.

In my worst nightmare they export GPIO lines using
the horrid ABI in /sys/gpio/*

In best case they use the GPIO character device or even
libgpiod.

But having a JTAG abstraction inside the kernel that can
grab a few lines for JTAG defined in a device tree, ACPI DSDT
or similar makes sense too, as it abstracts the hardware so the
JTAG client can then just open whatever /dev/jtag0 is on the machine
and go ahead without having to bother about what GPIO lines
are connected exactly where.

Yours,
Linus Walleij

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[patch v6 0/3] JTAG driver introduction Oleksandr Shamray <oleksandrs@mellanox.com> - 2017-08-22 18:20 +0200
  [patch v6 1/3] drivers: jtag: Add JTAG core driver Oleksandr Shamray <oleksandrs@mellanox.com> - 2017-08-22 18:20 +0200
  Re: [patch v6 0/3] JTAG driver introduction Linus Walleij <linus.walleij@linaro.org> - 2017-08-24 23:10 +0200
    Re: [patch v6 0/3] JTAG driver introduction Rick Altherr <raltherr@google.com> - 2017-08-24 23:40 +0200
      Re: [patch v6 0/3] JTAG driver introduction Linus Walleij <linus.walleij@linaro.org> - 2017-08-25 10:40 +0200
        Re: [patch v6 0/3] JTAG driver introduction Stuart Longland <stuartl@longlandclan.id.au> - 2017-08-25 11:00 +0200
          Re: [patch v6 0/3] JTAG driver introduction Rick Altherr <raltherr@google.com> - 2017-08-25 19:00 +0200
          Re: [patch v6 0/3] JTAG driver introduction Linus Walleij <linus.walleij@linaro.org> - 2017-08-28 00:30 +0200
        Re: [patch v6 0/3] JTAG driver introduction Rick Altherr <raltherr@google.com> - 2017-08-25 19:00 +0200
          Re: [patch v6 0/3] JTAG driver introduction Linus Walleij <linus.walleij@linaro.org> - 2017-08-28 00:40 +0200
            Re: [patch v6 0/3] JTAG driver introduction Rick Altherr <raltherr@google.com> - 2017-08-28 05:00 +0200

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