Date: Fri, 17 Apr 2015 10:55:37 +0100 From: Tom Jones <jones@sdf.org> To: freebsd-arm@freebsd.org Subject: Re: help with coding a loadable kernel module Message-ID: <20150417095536.GA38091@gmail.com> In-Reply-To: <9B835088-661C-456E-84A7-47BC1835C0CB@cs.huji.ac.il> References: <EDB591F5-E056-4E53-9ED2-2A2E571F319C@cs.huji.ac.il> <20150417080839.GO2743@home.opsec.eu> <9B835088-661C-456E-84A7-47BC1835C0CB@cs.huji.ac.il>
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On Fri, Apr 17, 2015 at 12:15:33PM +0300, Daniel Braniss wrote: > > > On Apr 17, 2015, at 11:08 AM, Kurt Jaeger <lists@opsec.eu> wrote: > > > > Hi! > > > >> 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? > > > > Are you aware of this book ? > > > > http://www.nostarch.com/bsddrivers.htm <http://www.nostarch.com/bsddrivers.htm>; > > 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? I don't think it does. spibus is very simple, there is one interface call SPIBUS_TRANSFER(device_t, device_t, strcut spi_command); struct spi_command { void *tx_cmd; uint32_t tx_cmd_sz; void *rx_cmd; uint32_t rx_cmd_sz; void *tx_data; uint32_t tx_data_sz; void *rx_data; uint32_t rx_data_sz; }; The rx and tx buffers need to be the same size. I there isn't an interface for configuring spibuses, the bcm2835_spi driver uses sysctl's directly to set clock speed and other configuration. I imagine the other drivers are similar or don't offer config. I can also assume you have hardware for the rfid. If not you might be able to find a reader that is supported by libnfc[1] which supports the rfid tags you need to use. [0]: svnweb.freebsd.org/base/head/sys/dev/spibus [1]: nfc-tools.org -- Tom @adventureloop adventurist.me #pragma summon cthulhu :wq
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