[PATCH v3 1/2] media: rcar-isp: distinguish absent cores from registration failures

[Myeonghun Pak <mhun512@gmail.com>]

risp_probe() interprets -ENODEV from risp_core_probe() as an absent
optional core and continues with the channel selector. Keep that result
for the existing resource-setup fallback, but distinguish it from a
failure after core resources have been initialized.

The following patch moves the core IRQ request after RPPX1 and the
registration state have been initialized. If that request returns
-ENODEV, its error path releases RPPX1 and the VSPX device reference.
Passing -ENODEV back unchanged would make the parent continue probing,
although core->base still indicates a core whose resources have already
been released.

Translate -ENODEV to -ENXIO at the registration error exit, after the
existing cleanup. The parent can then handle the failure using only the
return value, without inspecting core->base. Leave all resource-setup
results unchanged, including the existing fallback when VSPX information
is absent.

This prepares the error handling for the IRQ lifetime fix in the next
patch; it does not depend on an existing -ENODEV return from the V4L2
registration helpers.

This issue was identified during our ongoing research while reviewing
kernel code.

Suggested-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Assisted-by: LLM
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
---
Changes in v3:
- Express the distinction in the return value, as suggested by Niklas,
  instead of checking core->base in the caller.
- Translate -ENODEV only after resource setup has succeeded, keeping
  existing resource-setup and channel-selector fallback behavior.
- Describe this patch as a prerequisite for the IRQ registration move.

Changes in v2:
- Split the error-handling change out of the IRQ lifetime fix.

v2: https://lore.kernel.org/r/20261015004159.2202899-1-mhun512@gmail.com
v1: https://lore.kernel.org/r/20261011214448.2043581-1-mhun512@gmail.com

Compile-tested with Clang 22.1.2, W=1 (arm64). No runtime testing.

 drivers/media/platform/renesas/rcar-isp/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/renesas/rcar-isp/core.c b/drivers/media/platform/renesas/rcar-isp/core.c
index 586a5adbedfa8..373d9ca9374fe 100644
--- a/drivers/media/platform/renesas/rcar-isp/core.c
+++ b/drivers/media/platform/renesas/rcar-isp/core.c
@@ -894,7 +894,8 @@ int risp_core_probe(struct rcar_isp_core *core, struct platform_device *pdev,
 err_destroy_rpp:
 	rppx1_destroy(core->rpp);
 	put_device(core->vspx.dev);
-	return ret;
+	/* Do not report a registration failure as an absent core. */
+	return ret == -ENODEV ? -ENXIO : ret;
 }
 
 void risp_core_remove(struct rcar_isp_core *core)