Date: Fri, 17 Apr 2015 16:26:04 +0300 From: Daniel Braniss <danny@cs.huji.ac.il> To: Ian Lepore <ian@freebsd.org> Cc: Tom Jones <jones@sdf.org>, freebsd-arm@freebsd.org Subject: Re: help with coding a loadable kernel module Message-ID: <C6A90444-22F4-4EDF-BE3D-C384F61BB0B4@cs.huji.ac.il> In-Reply-To: <1429276417.1182.71.camel@freebsd.org> References: <EDB591F5-E056-4E53-9ED2-2A2E571F319C@cs.huji.ac.il> <20150417080839.GO2743@home.opsec.eu> <9B835088-661C-456E-84A7-47BC1835C0CB@cs.huji.ac.il> <20150417095536.GA38091@gmail.com> <32D7EBD3-813E-4062-8A06-ED8E82BA50DA@cs.huji.ac.il> <1429276417.1182.71.camel@freebsd.org>
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> On Apr 17, 2015, at 4:13 PM, Ian Lepore <ian@freebsd.org> wrote: >=20 > On Fri, 2015-04-17 at 13:46 +0300, Daniel Braniss wrote: >>> On Apr 17, 2015, at 12:55 PM, Tom Jones <jones@sdf.org> wrote: >>>=20 >>> On Fri, Apr 17, 2015 at 12:15:33PM +0300, Daniel Braniss wrote: >>>>=20 >>>>> On Apr 17, 2015, at 11:08 AM, Kurt Jaeger <lists@opsec.eu> wrote: >>>>>=20 >>>>> Hi! >>>>>=20 >>>>>> I know I'm embarking on a dangerous trip, but I want to use a = Raspberry Pi >>>>>> and or a BeagleBone to read (and write) RFID cards. >>>>>> Since a driver is needed to use the spibus, I have 2 options = while >>>>>> developing: >>>>> [...] >>>>>> So before I give up on option 2, is there some examples/help? >>>>>=20 >>>>> Are you aware of this book ? >>>>>=20 >>>>> http://www.nostarch.com/bsddrivers.htm = <http://www.nostarch.com/bsddrivers.htm>; >>>>=20 >>>> no, but before I spend more money (this is getting expensive :-), >>>> does it explain how to write a loadable module that needs to to = talk >>>> to a spibus?=20 >>>=20 >>> I don't think it does. >>>=20 >>> spibus is very simple, there is one interface call >>>=20 >>> SPIBUS_TRANSFER(device_t, device_t, strcut spi_command); >>>=20 >>=20 >> chicken and egg issue :-), what device_t dev should I use? >> it must point to the spibus =E2=80=A6 >=20 > Your device will be a child of the spibus, and it is the bus that it=E2=80=99s the =E2=80=98child of=E2=80=99 that I have problems. this = will be a loadable module, so it will have to tell the parent that he is no longer an orphan :-) > implements the SPIBUS_TRANSFER() method, so it's the bus's device_t = that > needs to be passed as the first parameter in the call (if it were C++ = it > would be the "this" pointer -- this stuff is OO implemented in = plain-C). >> =46rom your driver, something like: >=20 > SPIBUS_TRANSFER(device_get_parent(sc->sc_dev), sc->sc_dev, cmdptr); >=20 > I haven't got time this morning to put together a complete example of > how to add a module to the build, but the process is basically along = the > lines of... >=20 > Add a new directory to sys/dev for your driver just like you were > going to compile it into the kernel. Then in sys/modules find another > simple driver, copy it to a new directory, and change the names of > things in the makefile so that it refers to your new dir/files in > sys/dev. You can set MODULES_OVERRIDE=3Dyournew_dirname on the make > command line or in your kernel config to make it compile. >=20 I have that, even figured out how to cross compile and use the make = buildenv. it=E2=80=99s great! I can compile outside the source tree too. thanks, danny
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