6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Titus Rwantare <titusr@xxxxxxxxxx>
[ Upstream commit 6b6e2e8fd0de3fa7c6f4f8fe6841b01770b2e7bc ]
The `pmbus_identify()` function fails to correctly determine the number
of supported pages on PMBus devices. This occurs because `info->pages`
is implicitly zero-initialised, and `pmbus_set_page()` does not perform
writes to the page register if `info->pages` is not yet initialised.
Without this patch, `info->pages` is always set to the maximum after
scanning.
This patch initialises `info->pages` to `PMBUS_PAGES` before the probing
loop, enabling `pmbus_set_page()` writes to make it out onto the bus
correctly identifying the number of pages. `PMBUS_PAGES` seemed like a
reasonable non-zero number because that's the current result of the
identification process.
Testing was done with a PMBus device in QEMU.
Signed-off-by: Titus Rwantare <titusr@xxxxxxxxxx>
Fixes: 442aba78728e7 ("hwmon: PMBus device driver")
Link: https://lore.kernel.org/r/20250227222455.2583468-1-titusr@xxxxxxxxxx
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/hwmon/pmbus/pmbus.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/hwmon/pmbus/pmbus.c b/drivers/hwmon/pmbus/pmbus.c
index d0d386990af5e..6366610a90827 100644
--- a/drivers/hwmon/pmbus/pmbus.c
+++ b/drivers/hwmon/pmbus/pmbus.c
@@ -103,6 +103,8 @@ static int pmbus_identify(struct i2c_client *client,
if (pmbus_check_byte_register(client, 0, PMBUS_PAGE)) {
int page;
+ info->pages = PMBUS_PAGES;
+
for (page = 1; page < PMBUS_PAGES; page++) {
if (pmbus_set_page(client, page, 0xff) < 0)
break;
--
2.39.5
