trying to understand the device model

trying to understand the device model

[Hua Yu Yang]

hi

sorry for spam if this is actually just naive.

i'm new to linux kernel driver module and planning to write a small
driver module for gpio test, here is what confuses me:

1. in the kernel module programming guide from tldp.org, a device is
registered with system by major and minor numbers but in recent kernel
source( i'm working with 2.6.28.10 ), the files under
Documentation/driver-model/ seem to introduce a whole new set of
models, also in kernel source, gpiolib and plat-omap/gpio.c seem to
follow the new models. i'm not sure if the way described in kernel
module programming guide is still valid for recent kernels.

2. for your information, i want to write a simple driver based on gpio
interface described in Documentation/gpio.txt and implement a 8-bit
read function as well as an interrupt handler, sort of using gpios to
emulate a parallel port. this is just a workaround for lacking access
to camera interface on IGEPv2 board, so no need to consider
portability or whatsoever, is there any problem for me to just use
module_init() and module_exit(), as is shown in the kernel module
programming guide, instead of going into all those add/remove classes,
buses, interfaces?

thanks in advance!

-- 
Huayu Yang

Re: trying to understand the device model

[Felipe Balbi]

On Wed, Mar 24, 2010 at 05:43:38PM +0100, ext Hua Yu Yang wrote:
>hi
>
>sorry for spam if this is actually just naive.
>
>i'm new to linux kernel driver module and planning to write a small
>driver module for gpio test, here is what confuses me:
>
>1. in the kernel module programming guide from tldp.org, a device is
>registered with system by major and minor numbers but in recent kernel
>source( i'm working with 2.6.28.10 ), the files under

that's not recent at all :-s Could you move to current linux-omap git ?

>Documentation/driver-model/ seem to introduce a whole new set of
>models, also in kernel source, gpiolib and plat-omap/gpio.c seem to
>follow the new models. i'm not sure if the way described in kernel
>module programming guide is still valid for recent kernels.

you should try to use current kernels.

>2. for your information, i want to write a simple driver based on gpio
>interface described in Documentation/gpio.txt and implement a 8-bit
>read function as well as an interrupt handler, sort of using gpios to
>emulate a parallel port. this is just a workaround for lacking access
>to camera interface on IGEPv2 board, so no need to consider
>portability or whatsoever, is there any problem for me to just use
>module_init() and module_exit(), as is shown in the kernel module
>programming guide, instead of going into all those add/remove classes,
>buses, interfaces?

I believe you'll like to look at the platform_driver structures and make 
a driver that claims the gpios you need and sets correct direction/value 
when needed.

-- 
balbi