Re: [PATCH RESEND v4 06/10] PM: EM: Implement em_nl_get_pds_doit()

[Lukasz Luba <lukasz.luba@arm.com>]

On 9/21/25 04:19, Changwoo Min wrote:
> When a userspace requests EM_CMD_GET_PDS, the kernel responds with
> information on all performance domains. The message format of the
> response is as follows:
> 
> EM_A_PDS_PD (NLA_NESTED)*
>      EM_A_PD_PD_ID (NLA_U32)
>      EM_A_PD_FLAGS (NLA_U64)
>      EM_A_PD_CPUS (NLA_STRING)
> 
> where EM_A_PDS_PD can be repeated as many times as there are performance
> domains, and EM_A_PD_CPUS is a hexadecimal string representing a CPU
> bitmask.
> 
> Signed-off-by: Changwoo Min <changwoo@igalia.com>
> ---
>   kernel/power/em_netlink.c | 82 ++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 81 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/power/em_netlink.c b/kernel/power/em_netlink.c
> index f3fbfeff29a4..31b27c6fe3c9 100644
> --- a/kernel/power/em_netlink.c
> +++ b/kernel/power/em_netlink.c
> @@ -17,9 +17,89 @@
>   #include "em_netlink.h"
>   #include "em_netlink_autogen.h"
>   
> +#define EM_A_PD_CPUS_LEN		256
> +
> +/*************************** Command encoding ********************************/
> +static int __em_nl_get_pd_size(struct em_perf_domain *pd, void *data)
> +{
> +	char cpus_buf[EM_A_PD_CPUS_LEN];
> +	int *tot_msg_sz = data;
> +	int msg_sz, cpus_sz;
> +
> +	cpus_sz = snprintf(cpus_buf, sizeof(cpus_buf), "%*pb",
> +			   cpumask_pr_args(to_cpumask(pd->cpus)));
> +
> +	msg_sz = nla_total_size(0) +			/* EM_A_PDS_PD */
> +		 nla_total_size(sizeof(u32)) +		/* EM_A_PD_PD_ID */
> +		 nla_total_size_64bit(sizeof(u64)) +	/* EM_A_PD_FLAGS */
> +		 nla_total_size(cpus_sz);		/* EM_A_PD_CPUS */
> +
> +	*tot_msg_sz += nlmsg_total_size(genlmsg_msg_size(msg_sz));
> +	return 0;
> +}
> +
> +static int __em_nl_get_pd(struct em_perf_domain *pd, void *data)
> +{
> +	char cpus_buf[EM_A_PD_CPUS_LEN];
> +	struct sk_buff *msg = data;
> +	struct nlattr *entry;
> +
> +	entry = nla_nest_start(msg, EM_A_PDS_PD);
> +	if (!entry)
> +		goto out_cancel_nest;
> +
> +	if (nla_put_u32(msg, EM_A_PD_PD_ID, pd->id))
> +		goto out_cancel_nest;
> +
> +	if (nla_put_u64_64bit(msg, EM_A_PD_FLAGS, pd->flags, EM_A_PD_PAD))
> +		goto out_cancel_nest;
> +
> +	snprintf(cpus_buf, sizeof(cpus_buf), "%*pb",
> +		 cpumask_pr_args(to_cpumask(pd->cpus)));
> +	if (nla_put_string(msg, EM_A_PD_CPUS, cpus_buf))
> +		goto out_cancel_nest;
> +
> +	nla_nest_end(msg, entry);
> +
> +	return 0;
> +
> +out_cancel_nest:
> +	nla_nest_cancel(msg, entry);
> +
> +	return -EMSGSIZE;
> +}
> +
>   int em_nl_get_pds_doit(struct sk_buff *skb, struct genl_info *info)
>   {
> -	return -EOPNOTSUPP;
> +	struct sk_buff *msg;
> +	void *hdr;
> +	int cmd = info->genlhdr->cmd;
> +	int ret = -EMSGSIZE, msg_sz = 0;
> +
> +	for_each_em_perf_domain(__em_nl_get_pd_size, &msg_sz);
> +
> +	msg = genlmsg_new(msg_sz, GFP_KERNEL);
> +	if (!msg)
> +		return -ENOMEM;
> +
> +	hdr = genlmsg_put_reply(msg, info, &em_nl_family, 0, cmd);
> +	if (!hdr)
> +		goto out_free_msg;
> +
> +	ret = for_each_em_perf_domain(__em_nl_get_pd, msg);
> +	if (ret)
> +		goto out_cancel_msg;
> +
> +	genlmsg_end(msg, hdr);
> +
> +	return genlmsg_reply(msg, info);
> +
> +out_cancel_msg:
> +	genlmsg_cancel(msg, hdr);
> +out_free_msg:
> +	nlmsg_free(msg);
> +
> +	return ret;
>   }
>   
>   int em_nl_get_pd_table_doit(struct sk_buff *skb, struct genl_info *info)

LGTM,

Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>