5.4-stable review patch. If anyone has any objections, please let me know.
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From: Titus Rwantare titusr@google.com
[ 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@google.com Fixes: 442aba78728e7 ("hwmon: PMBus device driver") Link: https://lore.kernel.org/r/20250227222455.2583468-1-titusr@google.com Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c0bc43d010186..81d4e9e85d3ea 100644 --- a/drivers/hwmon/pmbus/pmbus.c +++ b/drivers/hwmon/pmbus/pmbus.c @@ -101,6 +101,8 @@ 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) < 0) break;