On Monday 31 March 2008 14:55:48 Bernd Büttner wrote:
> Bongani Hlope schrieb:
> > On Monday 31 March 2008 13:47:23 Bernd Büttner wrote:
> >> Bongani Hlope schrieb:
> >
> > 8<
> >
> >>> You really shouldn't be doing that in a module, that is why those
> >>> symbols are not exported. But if you really insist on reading/writing a
> >>> file in a kernel module look here:
> >>> http://www.linuxjournal.com/article/8110 it has both the lengthy
> >>> warning and examples of how to do it if you insist on doing the "wrong"
> >>> thing
> >>
> >> Thank you for the hint.
> >> I read the article and understand the problems.
> >> But I don't want to read from a file. I just want to read and write
> >> single bytes from and to a qspi-device. If I don't want to rewrite the
> >> qspi functions I have to call the qspi-driver.
> >> So what I'm searching for is a way to read/write a qspi-device from
> >> kernel mode without the indirection through user-mode.
> >
> > What device does you module drive?
>
> I have a device driver which handles digital and analog i/o. Most of them
> are located at pins of the coldfire cpu, some of them are behind the qspi
> bus. All data-ports are scanned in a settable time intervall and
> represented to user-space as a data field. User-space doesn't know whether
> data are located behind qspi or not. The hardware is flexible (no
> hotplugging), so the driver has a configuration area which is loaded from a
> flash device during startup, this is the reason for loadable modules.
What makes this setup difficult is the lack of a SPI salve-device in Linux...
Your module needs to be both the Digital-Analog I/O driver and SPI driver.
The SPI part will communicate with the coldfire qspi-driver:
e.g.
struct adio {
struct spi_device *spi;
struct my_device_type *device_type;
...
};
static int __devinit adio_probe(struct spi_device *spi)
{
struct adio *ad;
struct my_device_type *type_dev;
struct spi_message *msg;
struct spi_transfer *tx;
int err;
/* setup spi device*/
spi->bits_per_word = 8;
spi->mode = SPI_MODE_0;
err = spi_setup(spi);
if(err < 0)
return err;
ad = kzalloc(sizeof(struct adio), GFP_KERNEL)
type_dev = /* allocate ram for you device, e.g. input_allocate_device() or
kzalloc*/
if(!ad || !type_dev) {
err = -ENOMEM;
goto err_free_mem;
}
dev_set_drvdata(&spi->dev, ad); //SPI driver_data point's keeps track of your
driver
ad->spi = spi;
ad->device_type = type_dev;
/* setup the Digital-Analog IO device*/
...
return 0;
err_free_mem:
/*free your device memory e.g. input_free_device or kfree*/
kfree(ad);
return err;
}
static int __devexit adio_remove(struct spi_device *spi)
{
struct adio *ad = dev_get_drvdata(&spi->dev);
/*un-register your device e.g. input_unregister_device(ad->device_type)*/
kfree(ad);
return 0;
}
static struct spi_driver adio_driver = {
.driver = {
.name = "DigAnalogIO",
.bus = &spi_bus_tyep,
.owner = THID_MODULE,
},
.probe = adio_probe,
.remove = adio_remove,
};
static int __init adio_init(void)
{
return spi_register_driver(&adio_driver);
}
module_init(adio_init);
static void __exit adio_exit(void)
{
spi_unregister_driver(&adio_driver);
}
Then on the current receiving end do the following
static in adio_rx(void *adio)
{
struct spi_message *msg;
....
/* build your message here */
spi_sync(msg); //send
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