Hello everyone -
I am developing an embedded ppc system using a 2.4 series kernel and I
have a question regarding hardware drivers.
I have 4 LEDs connected to a GPIO port. Each LED is controlled by a bit
on the I/O port - set a bit to zero to turn the LED on, set the bit to one
to turn the LED off. The state of the bits are readable, so
read-modify-write works. The GPIO port is implemented with a Xilinx IP
module and I have a driver available. The Xilinx driver supports multiple
GPIO ports.
I have a driver available for the heartbeat LED ('status_led' by Wolfgang
Denk) that works.
Now to the question:
I wish to use one of the four LEDs as a 'heartbeat' and the remainder as
user LEDs. Since all LEDs are accessed using the same hardware resource,
the Linux heartbeat driver and the user GPIO driver will have to
arbitrate. I would like to separate the status led (heartbeat) driver
from the GPIO driver as much as I can. Is there an effective approach for
doing this? I think I could brute-force things by simply combining the
GPIO and status LED drivers and then tell the 'unified' driver which LED
to use as the heartbeat, but that approach eliminates the benefits of
using existing drivers 'as-is', among other things.
I'm thinking that what I need to be able to do is give each driver access
to a mutex that the drivers can then use to coordinate access to the
hardware, but I'm not sure how to set up the mutex or where to put the
code that does the initialization and mapping for the hardware access.
Keith
