Analog Digital Converter - ADS1256 extreme newbie questions

["Flávio Alberto Lopes Soares" <flavioalsoares-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hello all,
I'm working 9 years as a Linux C/C++ programmer but I spent 99,9% of this
time working in user space programming, now I need to write a driver to use
the ADS1256 Analog-Digital converter (
http://focus.ti.com/docs/prod/folders/print/ads1256.html ) in an ARM board
using S3C2440 processor, my lecture start point
was Documentation/spi/spi-sumary from 2.6.32.2 kernel tree version and
drivers/misc/eeprom/at25.c code (this is an eeprom driver but I want look
the SPI general view), reading the text and the code I found some conceptual
doubts, my initial idea was create a character device driver and attach the
device read operation with a ADS1256 start lecture and pass the ADC channel
data to this device, this concept is correct ? There's some standard
interface to do this if my idea is wrong ?

Looking in at25.c in at25_probe(struct spi_device *spi) function this
"struct spi_device *spi" parameter represents the S3C2440 SPI controller and
came from SPI core subsystem ? If yes how the SPI controller knows that this
is an eeprom device in the snippet bellow ?
...
const struct spi_eeprom *chip;
...
/* Chip description */
chip = spi->dev.platform_data;

who provides this platform_data structure and who knows it must be a struct
spi_eeprom object ?

Thanks for all help

Flávio Alberto Lopes Soares
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