linux-kernel - Re: [PATCH net-next 2/3] dpll: add dpll

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Message-ID: <0179717b-9567-4f3d-a521-6988c2d21ba6@linux.dev>
Date: Mon, 12 Jan 2026 11:35:51 +0000
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Ivan Vecera <ivecera@...hat.com>, netdev@...r.kernel.org
Cc: Donald Hunter <donald.hunter@...il.com>, Jakub Kicinski
 <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>,
 Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
 Jiri Pirko <jiri@...nulli.us>,
 Prathosh Satish <Prathosh.Satish@...rochip.com>, Petr Oros
 <poros@...hat.com>, linux-kernel@...r.kernel.org,
 Michal Schmidt <mschmidt@...hat.com>
Subject: Re: [PATCH net-next 2/3] dpll: add dpll_device op to set working mode

On 12/01/2026 10:14, Ivan Vecera wrote:
> Currently, userspace can retrieve the DPLL working mode but cannot
> configure it. This prevents changing the device operation, such as
> switching from manual to automatic mode and vice versa.
> 
> Add a new callback .mode_set() to struct dpll_device_ops. Extend
> the netlink policy and device-set command handling to process
> the DPLL_A_MODE attribute.  Update the netlink YAML specification
> to include the mode attribute in the device-set operation.
> 
> Signed-off-by: Ivan Vecera <ivecera@...hat.com>
> ---
>   Documentation/netlink/specs/dpll.yaml |  1 +
>   drivers/dpll/dpll_netlink.c           | 44 +++++++++++++++++++++++++++
>   drivers/dpll/dpll_nl.c                |  1 +
>   include/linux/dpll.h                  |  2 ++
>   4 files changed, 48 insertions(+)
> 
> diff --git a/Documentation/netlink/specs/dpll.yaml b/Documentation/netlink/specs/dpll.yaml
> index 78d0724d7e12c..b55afa77eac4b 100644
> --- a/Documentation/netlink/specs/dpll.yaml
> +++ b/Documentation/netlink/specs/dpll.yaml
> @@ -550,6 +550,7 @@ operations:
>           request:
>             attributes:
>               - id
> +            - mode
>               - phase-offset-monitor
>               - phase-offset-avg-factor
>       -
> diff --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c
> index d6a0e272d7038..37ca90ab841bd 100644
> --- a/drivers/dpll/dpll_netlink.c
> +++ b/drivers/dpll/dpll_netlink.c
> @@ -853,6 +853,45 @@ int dpll_pin_change_ntf(struct dpll_pin *pin)
>   }
>   EXPORT_SYMBOL_GPL(dpll_pin_change_ntf);
>   
> +static int
> +dpll_mode_set(struct dpll_device *dpll, struct nlattr *a,
> +	      struct netlink_ext_ack *extack)
> +{
> +	const struct dpll_device_ops *ops = dpll_device_ops(dpll);
> +	enum dpll_mode mode = nla_get_u32(a), old_mode;
> +	DECLARE_BITMAP(modes, DPLL_MODE_MAX) = { 0 };

I believe the size of bitmap should be DPLL_MODE_MAX + 1 or
__DPLL_MODE_MAX?

> +	int ret;
> +
> +	if (!(ops->mode_set && ops->supported_modes_get)) {
> +		NL_SET_ERR_MSG_ATTR(extack, a,
> +				    "dpll device does not support mode switch");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	ret = ops->mode_get(dpll, dpll_priv(dpll), &old_mode, extack);
> +	if (ret) {
> +		NL_SET_ERR_MSG(extack, "unable to get current mode");
> +		return ret;
> +	}
> +
> +	if (mode == old_mode)
> +		return 0;
> +
> +	ret = ops->supported_modes_get(dpll, dpll_priv(dpll), modes, extack);
> +	if (ret) {
> +		NL_SET_ERR_MSG(extack, "unable to get supported modes");
> +		return ret;
> +	}
> +
> +	if (!test_bit(mode, modes)) {
> +		NL_SET_ERR_MSG(extack,
> +			       "dpll device does not support requested mode");
> +		return -EINVAL;
> +	}
> +
> +	return ops->mode_set(dpll, dpll_priv(dpll), mode, extack);
> +}
> +
>   static int
>   dpll_phase_offset_monitor_set(struct dpll_device *dpll, struct nlattr *a,
>   			      struct netlink_ext_ack *extack)
> @@ -1808,6 +1847,11 @@ dpll_set_from_nlattr(struct dpll_device *dpll, struct genl_info *info)
>   	nla_for_each_attr(a, genlmsg_data(info->genlhdr),
>   			  genlmsg_len(info->genlhdr), rem) {
>   		switch (nla_type(a)) {
> +		case DPLL_A_MODE:
> +			ret = dpll_mode_set(dpll, a, info->extack);
> +			if (ret)
> +				return ret;
> +			break;
>   		case DPLL_A_PHASE_OFFSET_MONITOR:
>   			ret = dpll_phase_offset_monitor_set(dpll, a,
>   							    info->extack);
> diff --git a/drivers/dpll/dpll_nl.c b/drivers/dpll/dpll_nl.c
> index 36d11ff195df4..a2b22d4921142 100644
> --- a/drivers/dpll/dpll_nl.c
> +++ b/drivers/dpll/dpll_nl.c
> @@ -45,6 +45,7 @@ static const struct nla_policy dpll_device_get_nl_policy[DPLL_A_ID + 1] = {
>   /* DPLL_CMD_DEVICE_SET - do */
>   static const struct nla_policy dpll_device_set_nl_policy[DPLL_A_PHASE_OFFSET_AVG_FACTOR + 1] = {
>   	[DPLL_A_ID] = { .type = NLA_U32, },
> +	[DPLL_A_MODE] = NLA_POLICY_RANGE(NLA_U32, 1, 2),
>   	[DPLL_A_PHASE_OFFSET_MONITOR] = NLA_POLICY_MAX(NLA_U32, 1),
>   	[DPLL_A_PHASE_OFFSET_AVG_FACTOR] = { .type = NLA_U32, },
>   };
> diff --git a/include/linux/dpll.h b/include/linux/dpll.h
> index 912a2ca3e0ee7..c6d0248fa5273 100644
> --- a/include/linux/dpll.h
> +++ b/include/linux/dpll.h
> @@ -20,6 +20,8 @@ struct dpll_pin_esync;
>   struct dpll_device_ops {
>   	int (*mode_get)(const struct dpll_device *dpll, void *dpll_priv,
>   			enum dpll_mode *mode, struct netlink_ext_ack *extack);
> +	int (*mode_set)(const struct dpll_device *dpll, void *dpll_priv,
> +			enum dpll_mode mode, struct netlink_ext_ack *extack);
>   	int (*supported_modes_get)(const struct dpll_device *dpll,
>   				   void *dpll_priv, unsigned long *modes,
>   				   struct netlink_ext_ack *extack);