tools/gpio: add the gpio-hammer tool

The gpio-hammer is used from userspace as an example of how
to retrieve a GPIO handle for one or several GPIO lines and
hammer the outputs from low to high and back again. It will
pulse the selected lines once per second for a specified
number of times or indefinitely if no loop count is
supplied.

Example output:
$ gpio-hammer -n gpiochip0 -o5 -o6 -o7
Hammer lines [5, 6, 7] on gpiochip0, initial states: [1, 1, 1]
[-] [5: 0, 6: 0, 7: 0]

Tested-by: Michael Welling <mwelling@ieee.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/tools/gpio/Makefile b/tools/gpio/Makefile
index c155d6bc47a7..aea23949054e 100644
--- a/tools/gpio/Makefile
+++ b/tools/gpio/Makefile
@@ -1,12 +1,13 @@
 CC = $(CROSS_COMPILE)gcc
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE
 
-all: lsgpio
+all: lsgpio gpio-hammer
 
 lsgpio: lsgpio.o gpio-utils.o
+gpio-hammer: gpio-hammer.o gpio-utils.o
 
 %.o: %.c gpio-utils.h
 
 .PHONY: clean
 clean:
-        rm -f *.o lsgpio
+        rm -f *.o lsgpio gpio-hammer