Re: [PATCH v2] driver core: Fix bus_type.match() error handling

Marek Szyprowski
2022-08-25T09:23:03Z

On 15.08.2022 23:19, Isaac J. Manjarres wrote:
> Both __device_attach_driver() and __driver_attach() check the return
> code of the bus_type.match() function to see if the device needs to be
> added to the deferred probe list. After adding the device to the list,
> the logic attempts to bind the device to the driver anyway, as if the
> device had matched with the driver, which is not correct.
>
> If __device_attach_driver() detects that the device in question is not
> ready to match with a driver on the bus, then it doesn't make sense for
> the device to attempt to bind with the current driver or continue
> attempting to match with any of the other drivers on the bus. So, update
> the logic in __device_attach_driver() to reflect this.
>
> If __driver_attach() detects that a driver tried to match with a device
> and that results in any error, then the driver should not attempt to bind
> with the device. However, the driver can still attempt to match and bind
> with other devices on the bus, as drivers can be bound to multiple
> devices. So, update the logic in __driver_attach() to reflect this.
>
> Cc: Saravana Kannan <saravanak@google.com>
> Cc: stable@kernel.org
> Fixes: 656b8035b0ee ("ARM: 8524/1: driver cohandle -EPROBE_DEFER from bus_type.match()")
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>

This fixes the boot issue observed on Qualcomm APQ8016 based DragonBoard
410c, which I've missed while testing the "amba: Remove deferred device
addition" patch. Feel free to add:

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---
> drivers/base/dd.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> v1 -> v2:
> - Fixed the logic in __driver_attach() to allow a driver to continue
> attempting to match and bind with devices in case of any error, not
> just probe deferral.
>
> Guenter,
>
> Can you please give test this patch to make sure it still works for you?
>
> Thanks,
> Isaac
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 70f79fc71539..453eb19a9a27 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -881,6 +881,11 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
> dev_dbg(dev, "Device match requests probe deferral\n");
> dev->can_match = true;
> driver_deferred_probe_add(dev);
> + /*
> + * Device can't match with a driver right now, so don't attempt
> + * to match or bind with other drivers on the bus.
> + */
> + return ret;
> } else if (ret < 0) {
> dev_dbg(dev, "Bus failed to match device: %d\n", ret);
> return ret;
> @@ -1120,9 +1125,18 @@ static int __driver_attach(struct device *dev, void *data)
> dev_dbg(dev, "Device match requests probe deferral\n");
> dev->can_match = true;
> driver_deferred_probe_add(dev);
> + /*
> + * Driver could not match with device right now, but may match
> + * with another device on the bus.
> + */
> + return 0;
> } else if (ret < 0) {
> dev_dbg(dev, "Bus failed to match device: %d\n", ret);
> - return ret;
> + /*
> + * Driver could not match with device, but may match with
> + * another device on the bus.
> + */
> + return 0;
> } /* ret > 0 means positive match */
>
> if (driver_allows_async_probing(drv)) {

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland