[PATCH] firmware: arm_scmi: check return value of idr_find

[Kangjie Lu]

Thanks for Steven Price's review of this patch. In the current code,
idr_find won't return NULL because the SCMI_PROTOCOL_BASE id must 
exist. However, it might return NULL in the future code if the check
is on another node while processing the children in subsequent calls 
to scmi_mbox_chan_setup().
Therefore, the patch conservatively checks the return value and 
returns -EINVAL when it indeed failed.

Signed-off-by: Kangjie Lu <kjlu@xxxxxxx>
Reviewed-by: Steven Price <steven.price@xxxxxxx>
---
 drivers/firmware/arm_scmi/driver.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 8f952f2f1a29..35faa203d549 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -709,6 +709,8 @@ scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev, int prot_id)
 
 	if (scmi_mailbox_check(np)) {
 		cinfo = idr_find(&info->tx_idr, SCMI_PROTOCOL_BASE);
+		if (!cinfo)
+			return -EINVAL;
 		goto idr_alloc;
 	}
 
-- 
2.17.1