How to use spi device from another kernel module?

[Joel Fernandes]

On Tue, Dec 6, 2016 at 11:02 PM, Greg KH <greg at kroah.com> wrote:
> On Tue, Dec 06, 2016 at 09:12:24PM -0800, Joel Fernandes wrote:
>> On Tue, Dec 6, 2016 at 11:42 AM, Ran Shalit <ranshalit at gmail.com> wrote:
>> > Hello,
>> >
>> > I have spi device which is registered using spi_register_board_info(),
>> > and I would like to get a pointer to this device in some other kernel module.
>> >
>> > Is there a simple way to get a pointer to pointer to a device , so
>> > that we can use it from other module ? (something like i2c_get_adapter
>> > for i2c)
>>
>> Find out what's the SPI bus number (for the master) and the chip
>> select on that SPI master (for the SPI device)
>>
>> Then you can use bus_for_each_device on spi_bus_type and find the
>> spi_device you're looking for. See the following code for an example
>> of how to use bus_for_each_device:
>>
>> http://lxr.free-electrons.com/source/drivers/spi/spi.c#L524
>>
>> In your check function, just make sure your spi->master->bus_num is
>> the bus you want and the spi->chip_select is the chip select
>> corresponding to the device you want. If both these conditions are
>> satisfied, there you have your spi_device.
>
> Eeek, no, please never do that, use the proper spi apis to get your
> needed device.  They are there somewhere, using a "raw"
> bus_for_each_device is never the answer unless you are a bus and
> iterating over your own device list.

Yes I completely agree, maybe I assumed too much and thought he was
trying to do this for some quick debugging from some kernel module,
and was just looking for a quick and dirty way to get to a spi_device.
Was not really suggesting this for production code. :)

Regards,
Joel

>
> thanks,
>
> greg k-h