On 10/22/21 10:40 AM, Henk Medenblik wrote:
Hi Lars,
I don't think that the issue is here the two MODULE_DEVICE_TABLE
modaliases in my ltc6951 driver. I have them both for the
spi_device_id and also the of_device_id defined.
And I believe that if any of them would be missing, then manual
modprobe of the ltc6951 driver would fail too.
The table itself is used for the probing process. But the
MODULE_DEVICE_TABLE is only used to signal userspace that this module
handles the devices that are listed in the table. udev uses this
information to load the driver if necessary.
Manual loading will still work without the MODULE_DEVICE_TABLE. But of
course not without the table itself.
The issue is that it does not get automatically enumerated when my
custom spi controller get loaded (i can see after boot that the spi
controller is alive when looking into /proc/modules)
However, the spi slave device is not alive. The strange thing is that
this does work if I connect the spi slave to the onboard SPI
controller which resides inside the Zynq MPSoC.. (after putting the
ltc slave in the tree under that controller)
Ok, that's a bit odd that it works with the MPSoC controller. What I'd
do is check `/sys/bus/spi/devices/`. Your device will be there even if
driver has not been loaded. And then check the `modalias` and `uevent`
files of the device. Check if those files look different when using your
controller vs. the MPSoC.
- Lars
Regards
Henk
On 10/22/21 10:25 AM, Lars-Peter Clausen wrote:
On 10/22/21 9:55 AM, Henk Medenblik wrote:
Hi all,
I am using a custom SPI controller which I created in my Xilinx
MPSoC fpga part. On this custom spi controller bus I have one or
more SPI devices (in my case a custom LTC6951 driver) connected in
the devicetree under my spi controller.
Because the controller is custom, I wrote the SPI controller driver
and also some slave device drivers which seem to work.
These drivers are both created as out of tree loadable modules.
My issue is that at boot of my SocFPGA I can see that my SPI
controller driver is correctly loaded during the boot process but
the spi slave driver which is connected to my controller does not
get automatically loaded.
Therefore, I manually need to do a modprobe ltc6951.ko in my case
before the LTC6951 slave in my case is up and running.
So, it seems like if I do not really understand the spi slaves
enumeration process or there is something else that I am missing
here. I was under the assumption that the slaves automatically get
enumerated (they are put as slaves under my controller inside the
device tree) whenever it's master controller becomes alive.
Hi,
Modules are loaded by userspace, e.g. udev. It does so based on hints
that are embedded in the module, these are called MODALIASs. When
udev sees a device without a driver it will check all the modules to
see if they have a matching modalias for the driver and then load the
module.
In your driver you define the modalias usually using
MODULE_DEVICE_TABLE(type, table). E.g. for a SPI driver the type
would be spi and will take a reference to the spi_device_id table for
your driver. In addition if you are using devicetree you do the same
for the of_device_id table with `of` as the type.
- Lars
