Re: [PATCH net-next V4 4/6] devlink: Apply eswitch mode boot defaults

[Mark Bloch <mbloch@nvidia.com>]

On 02/07/2026 10:41, Paolo Abeni wrote:
> On 6/29/26 8:20 PM, Mark Bloch wrote:
>> Apply parsed devlink_eswitch_mode= defaults after devlink registration
>> and after successful reload.
>>
>> devl_register() may still be called before the device is ready for an
>> eswitch mode change, so keep a per-devlink delayed work item and pending
>> flag for the registration path. Registration queues the work, and the
>> worker tries to take the devlink instance lock.
>>
>> If the lock is busy, the worker requeues itself with a delay.
>>
>> For successful reloads that performed DRIVER_REINIT, devlink_reload()
>> already holds the devlink instance lock and the driver has completed
>> reload_up(). Clear pending work and apply the default directly from the
>> reload path instead of queueing work.
>>
>> If a user sets eswitch mode through netlink before the pending
>> registration work runs, clear the pending flag so the queued default does
>> not override that user request. Cancel pending default apply work when
>> freeing the devlink instance.
>>
>> Signed-off-by: Mark Bloch <mbloch@nvidia.com>
>> ---
>>  net/devlink/core.c          | 198 +++++++++++++++++++++++++++++++-----
>>  net/devlink/dev.c           |   6 ++
>>  net/devlink/devl_internal.h |   5 +
>>  3 files changed, 182 insertions(+), 27 deletions(-)
>>
>> diff --git a/net/devlink/core.c b/net/devlink/core.c
>> index 5126509a9c4e..998e4ffd5dce 100644
>> --- a/net/devlink/core.c
>> +++ b/net/devlink/core.c
>> @@ -5,6 +5,7 @@
>>   */
>>  
>>  #include <linux/init.h>
>> +#include <linux/jiffies.h>
>>  #include <linux/list.h>
>>  #include <linux/slab.h>
>>  #include <linux/string.h>
>> @@ -22,8 +23,12 @@ DEFINE_XARRAY_FLAGS(devlinks, XA_FLAGS_ALLOC);
>>  
>>  static char *devlink_default_esw_mode_param;
>>  static bool devlink_default_esw_mode_match_all;
>> +static bool devlink_default_esw_mode_enabled;
>>  static enum devlink_eswitch_mode devlink_default_esw_mode;
>>  static LIST_HEAD(devlink_default_esw_mode_nodes);
>> +static struct workqueue_struct *devlink_default_esw_mode_wq;
>> +
>> +#define DEVLINK_DEFAULT_ESW_MODE_APPLY_DELAY msecs_to_jiffies(100)
>>  
>>  struct devlink_default_esw_mode_node {
>>  	struct list_head list;
>> @@ -166,6 +171,7 @@ static void __init devlink_default_esw_mode_nodes_clear(void)
>>  	}
>>  
>>  	devlink_default_esw_mode_match_all = false;
>> +	devlink_default_esw_mode_enabled = false;
>>  }
>>  
>>  static int __init devlink_default_esw_mode_parse(char *str)
>> @@ -192,14 +198,113 @@ static int __init devlink_default_esw_mode_parse(char *str)
>>  		return err;
>>  
>>  	err = devlink_default_esw_mode_handles_parse(handles);
>> -	if (err)
>> +	if (err) {
>>  		devlink_default_esw_mode_nodes_clear();
>> -	else
>> +	} else {
>>  		devlink_default_esw_mode = esw_mode;
>> +		devlink_default_esw_mode_enabled = true;
>> +	}
>>  
>>  	return err;
>>  }
>>  
>> +static bool devlink_default_esw_mode_match(struct devlink *devlink)
>> +{
>> +	const char *bus_name = devlink_bus_name(devlink);
>> +	const char *dev_name = devlink_dev_name(devlink);
>> +	struct devlink_default_esw_mode_node *node;
>> +
>> +	if (devlink_default_esw_mode_match_all)
>> +		return true;
>> +
>> +	node = devlink_default_esw_mode_node_find(bus_name, dev_name);
>> +	return !!node;
>> +}
>> +
>> +void devlink_default_esw_mode_apply(struct devlink *devlink)
>> +{
>> +	const struct devlink_ops *ops = devlink->ops;
>> +	int err;
>> +
>> +	devl_assert_locked(devlink);
>> +
>> +	if (!devlink_default_esw_mode_match(devlink))
>> +		return;
>> +
>> +	if (!ops->eswitch_mode_set) {
>> +		if (!devlink_default_esw_mode_match_all)
>> +			devl_warn(devlink,
>> +				  "devlink_eswitch_mode= selected this device but eswitch mode setting is not supported\n");
> 
> Not a very strong opinion on my side, but I *think* it would be more
> consistent to emit this warning even for devlink_default_esw_mode_match_all
> 

I kept it only for the explicit handle case intentionally.

With "*" most devlink instances are not expected
to support eswitch mode. In the current tree I see 9 drivers 
that do, and many more devlink users without it.

So warning for every unsupported instance in the "*" case would be noisy
and would look like errors for devices this knob was never meant for.

Mark

> /P
>