[PATCH 3/3] firmware: arm_ffa: Fix FFA device names for logical partitions

[Sudeep Holla]

Each physical partition can provide multiple services each with UUID.
Each such service can be presented as logical partition with a unique
combination of VM ID and UUID. The number of distinct UUID in a system
will be less than or equal to the number of logical partitions.

However, currently it fails to register more than one logical partition
or service within a physical partition as the device name contains only
VM ID while both VM ID and UUID are maintained in the partition information.
The kernel complains with the below message:

  | sysfs: cannot create duplicate filename '/devices/arm-ffa-8001'
  | CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.3.0-rc7 #8
  | Hardware name: FVP Base RevC (DT)
  | Call trace:
  |  dump_backtrace+0xf8/0x118
  |  show_stack+0x18/0x24
  |  dump_stack_lvl+0x50/0x68
  |  dump_stack+0x18/0x24
  |  sysfs_create_dir_ns+0xe0/0x13c
  |  kobject_add_internal+0x220/0x3d4
  |  kobject_add+0x94/0x100
  |  device_add+0x144/0x5d8
  |  device_register+0x20/0x30
  |  ffa_device_register+0x88/0xd8
  |  ffa_setup_partitions+0x108/0x1b8
  |  ffa_init+0x2ec/0x3a4
  |  do_one_initcall+0xcc/0x240
  |  do_initcall_level+0x8c/0xac
  |  do_initcalls+0x54/0x94
  |  do_basic_setup+0x1c/0x28
  |  kernel_init_freeable+0x100/0x16c
  |  kernel_init+0x20/0x1a0
  |  ret_from_fork+0x10/0x20
  | kobject_add_internal failed for arm-ffa-8001 with -EEXIST, don't try to
  | register things with the same name in the same directory.
  | arm_ffa arm-ffa: unable to register device arm-ffa-8001 err=-17
  | ARM FF-A: ffa_setup_partitions: failed to register partition ID 0x8001

By virtue of being random enough to avoid collisions when generated in a
distributed system, there is no way to compress UUID keys to the number
of bits required to identify each. We can eliminate '-' in the name but
it is not worth eliminating 4 bytes and add unnecessary logic for doing
that. Also v1.0 doesn't provide the UUID of the partitions which makes
it hard to use the same for the device name.

So to keep it simple, let us just append the index to the list of the
partitions obtained in response to FFA_PARTITION_INFO_GET to "arm-ffa" to
make up a unique device name.

Fixes: e781858488b9 ("firmware: arm_ffa: Add initial FFA bus support for device enumeration")
Reported-by: Lucian Paul-Trifu <lucian.paul-trifu at arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
---
 drivers/firmware/arm_ffa/driver.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 4aced2e5b772..39b912bbd7db 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -678,7 +678,7 @@ static void ffa_setup_partitions(void)
 		 * provides UUID here for each partition as part of the
 		 * discovery API and the same is passed.
 		 */
-		ffa_dev = ffa_device_register(&uuid, tpbuf->id, &ffa_drv_ops);
+		ffa_dev = ffa_device_register(&uuid, idx, &ffa_drv_ops);
 		if (!ffa_dev) {
 			pr_err("%s: failed to register partition ID 0x%x\n",
 			       __func__, tpbuf->id);

-- 
2.40.0