[uClinux-dev] coldfire pio driver

Tarkan Bas bas at acter.ch
Thu Mar 6 03:04:51 EST 2003

Hi Ron,

Ron Fial wrote:
> If this is for an embedded project, and there is only one program that will be setting and clearing the PIO port bits, then you can just do a direct read and write to the port data direction registers and to the port I/O-pins register.    This should take under 1 hour to implement.   It is best to keep an RAM variable 'image' of the port pins, change that, and write it out.
> If you have two or more programs that use the port, but each uses different pins, then a simple semaphore arangement could be used to prevent simultaneous read/writes by two programs at the same time.  This might take an afternoon depending on how you do the mutex stuff.  You would probably read/modify/write the pins to reduce the need for 'shared' variables between the programs.
> If you need interrupt handlers for high-speed read/analyze/write of port pins, then you really need a kernel driver with a simple open, close, ioctl and init routine, along with the proper /dev/pio node with a major and minor device number.  Figure 1-2 days if you have experience writing kernel drivers (this is a very simple driver).  Figure 1-2 weeks if you have never written a kernel driver before and need to buy Rubini's book  ("Linux Device Drivers, 2nd edition".    I think I have found the chapters available to read on the web, tho.   It is an excellent book.  Look around in /Linux-x.x.x/drivers/char for good examples of character oriented (not block-oriented) drivers.

this is actually what I want. A kernel driver with interrupt handlers
for coldfire M5249. I found a T6963 driver (as far as I see it can be
used in pio mode, too) in config.in file in /Linux-x.x.x/drivers/char
directory but no .c file for that driver. Maybe this could be what I
want. does someone know where is the C-file for T6963 driver.????

> If you have a budget to spend, and need the driver quickly, I', sure someone on the list would be able to quote you a price to create such a driver for you -- maybe even for free just for the experience.
>    Good Luck,
>    Ron Fial

Thanks for advice. 


>   At 05:23 PM 3/5/2003 +0100, you wrote:
> >Dear all,
> >
> >I am searching for a pio driver for coldfire MCF5249 (i.e for led and
> >button control). Does  any char driver exist allready which I can use as
> >a pio driver!
> >
> >regards,
> >
> >Tarkan
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> >
> >
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