Messages in this thread |  | | Date | Mon, 8 Jun 2009 08:36:36 +0200 | Subject | Re: driver model advice | From | Geert Uytterhoeven <> |
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On Mon, Jun 8, 2009 at 00:45, Alexander Clouter<alex@digriz.org.uk> wrote: > For a while I have been maintaining the TS-7800 mainline support[1] and > decided to attempt to properly address support for the FPGA on the > board. > > Currently the solution I'm using[2] is not very flexible and scalable as > for every device that is added the platform code grows with it. I also > think it's just not very pretty. > > I have been reading various sources of documentation regarding the > driver model and relevant sections in the LDD tomb and felt that making > the FPGA behave as a bus seemed a neat way to do things. > > A quick overview of the approach I'm using is that the bus code adds and > removes the devices depending on the bus's state ('online' or > 'offline'). When going online (or as new drivers are insmod'ed) the bus > decides if the 'discover' function should be executed depending on the > FPGA bitstream magic number and then if the driver's discover() function > decides the device is present it is added to the bus.
You can make it a separate bus...
> The code for my amendments can be found (it's 30kB hence why it's not > inline), it's been written against 2.6.30-rc7: > > http://stuff.digriz.org.uk/ts78xx-fpga/fpga-device-work.diff > > and the my .config file is: > > http://stuff.digriz.org.uk/ts78xx-fpga/ts78xx.config > > One thing that might make people 'queasy' is that there is some wrapper > code for platform drivers. Although all the examples I have coded up > use platform drivers and create platform devices, there are some drivers > that are non-platform based in the works (GPIO, AVR, ISA bus, etc). I > felt the appropriate approach was (bearing in mind that different FPGA > bitstreams implement possibly overlapping/partial duplicate > functionality) to use a platform wrapper, the platform device being a > child of my ts78xx-fgpa device.
... or you can make the ts78xx-fpga device a multi-function device (drivers/mfd).
(In case the mfd-ers read this: recently I've been looking at using the mfd code for Amiga Zorro expansion boards. As most Zorro boards are made from discrete components, several of them are actually multi-function devices, which prohibits me from just using zorro_driver).
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
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