On Tue, Aug 22, 2017 at 6:10 PM, Oleksandr Shamray <oleksandrs@xxxxxxxxxxxx> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
