linux-kernel - [PATCH 09/14] fsi: core: Fix legacy minor numbering

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Message-Id: <20230612195657.245125-10-eajames@linux.ibm.com>
Date:   Mon, 12 Jun 2023 14:56:52 -0500
From:   Eddie James <eajames@...ux.ibm.com>
To:     linux-fsi@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, jk@...abs.org, joel@....id.au,
        alistair@...ple.id.au, andrew@...id.au, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        devicetree@...r.kernel.org
Subject: [PATCH 09/14] fsi: core: Fix legacy minor numbering

From: Eddie James <eajames@...ibm.com>

The legacy minor numbering shifts the chip id too much,
resulting in ids that overlap with regular ids. Since there
are only 2 bits for 4 types, only shift the chip id by 2
to fit the legacy ids in their reserved space.

Signed-off-by: Eddie James <eajames@...ux.ibm.com>
---
 drivers/fsi/fsi-core.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index 47e47c16d5ed..ea280f149b3f 100644
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -934,8 +934,12 @@ static int __fsi_get_new_minor(struct fsi_slave *slave, enum fsi_dev_type type,
 
 	/* Check if we qualify for legacy numbering */
 	if (cid >= 0 && cid < 16 && type < 4) {
-		/* Try reserving the legacy number */
-		id = (cid << 4) | type;
+		/*
+		 * Try reserving the legacy number, which has 0 - 0x3f reserved
+		 * in the ida range. cid goes up to 0xf and type contains two
+		 * bits, so construct the id with the below two bit shift.
+		 */
+		id = (cid << 2) | type;
 		id = ida_simple_get(&fsi_minor_ida, id, id + 1, GFP_KERNEL);
 		if (id >= 0) {
 			*out_index = fsi_adjust_index(cid);
@@ -970,7 +974,8 @@ int fsi_get_new_minor(struct fsi_device *fdev, enum fsi_dev_type type,
 		int aid = of_alias_get_id(fdev->dev.of_node, fsi_dev_type_names[type]);
 
 		if (aid >= 0) {
-			int id = (aid << 4) | type;
+			/* Use the same scheme as the legacy numbers. */
+			int id = (aid << 2) | type;
 
 			id = ida_simple_get(&fsi_minor_ida, id, id + 1, GFP_KERNEL);
 			if (id >= 0) {
-- 
2.31.1