[PATCH] firmware: arm_ffa: Emit modalias for FF-A devices

[Abdellatif El Khlifi]

Hi Sudeep,

> In order to enable libkmod lookups for FF-A device objects to their
> corresponding module, add 'modalias' to the base attribute of FF-A
> devices.
> 
> Cc: Abdellatif El Khlifi <abdellatif.elkhlifi at arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
> ---

Tested-by: Abdellatif El Khlifi <abdellatif.elkhlifi at arm.com>

More details:

We used this patch to autoload Arm FF-A TEE kernel module [1].
Please have a look at the tests logs [2].

The logs show:

- The aliases exported in sysfs by the FF-A bus for each FF-A device
- modinfo output for arm-ffa-tee.ko which uses an alias pattern matching the alias exported by the bus driver
- mdev (the device manager) command autorun at boot time, searches for the modalias entries in sysfs and passes them to modprobe
- modprobe matches between the sysfs alias and the kernel module
- lsmod shows that the module was loaded automatically at boot time

Cheers,
Abdellatif

[1]: arm-ffa-tee.ko: https://gitlab.arm.com/linux-arm/linux-trusted-services
[2]: logs for the tests made

root at corstone1000-fvp:~# uname -r
6.4.14-yocto-standard
root at corstone1000-fvp:~# 
root at corstone1000-fvp:~# cat /sys/devices/arm-ffa-1/modalias 
arm_ffa:8001:486178e0-e7f8-11e3-bc5e-0002a5d5c51broot at corstone1000-fvp:~# 
root at corstone1000-fvp:~# cat /sys/devices/arm-ffa-2/modalias  
arm_ffa:8002:46bb39d1-b4d9-45b5-88ff-040027dab249root at corstone1000-fvp:~# 
root at corstone1000-fvp:~# cat /sys/devices/arm-ffa-3/modalias   
arm_ffa:8003:00000000-0000-0000-0000-000000000000root at corstone1000-fvp:~# 
root at corstone1000-fvp:~# 
root at corstone1000-fvp:~# modinfo /lib/modules/6.4.14-yocto-standard/updates/arm-ffa-tee.ko 
filename:       /lib/modules/6.4.14-yocto-standard/updates/arm-ffa-tee.ko
version:        1.1.2
license:        GPL v2
description:    Arm FF-A TEE driver
author:         Balint Dobszay <balint.dobszay at arm.com>
alias:          arm_ffa:*:*
srcversion:     693E15C4E73D08A57E02B1E
depends:        
name:           arm_ffa_tee
vermagic:       6.4.14-yocto-standard SMP preempt aarch64
root at corstone1000-fvp:~# 
root at corstone1000-fvp:~# 
root at corstone1000-fvp:~# grep modalias /etc/init.d/mdev -A 4
  find /sys/ -name modalias -print0 | \
    xargs -0 sort -u | \
    tr '\n' '\0' | \
    xargs -0 modprobe -abq
}
root at corstone1000-fvp:~# 
root at corstone1000-fvp:~# lsmod
Module                  Size  Used by
arm_ffa_tee            12288  -2
root at corstone1000-fvp:~#