[PATCH ath-next] wifi: ath12k: avoid dynamic alloc when parsing wmi tb

[Jeff Johnson]

On 3/9/2026 8:20 AM, Nicolas Escande wrote:

I have some nit comments...

> On each WMI message received from the hardware, we alloc a temporary array

note that not every WMI message handler uses this pattern.

> of WMI_TAG_MAX entries of type void *. This array is then populated with
> pointers of parsed structs depending on the WMI type, and then freed. This
> alloc can fail when memory pressure in the system is high enough.
> 
> Given the fact that it is scheduled in softirq with the system_bh_wq, we
> should not be able to parse more than one WMI message per CPU at any time

add hard stop .

> 
> So instead lets move to a per cpu allocated array, stored in the struct
> ath12k_base, that is reused accros calls. The ath12k_wmi_tlv_parse_alloc()

s/accros/across/

> is also renamed into / merged with ath12k_wmi_tlv_parse() as it no longer
> allocs memory but returns the existing per-cpu one.

note that imperative voice is preferred.

> 
> Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00218-QCAHKSWPL_SILICONZ-1
> 
> Signed-off-by: Nicolas Escande <nico.escande at gmail.com>
> ---
> changes from RFC:
>   - rebased on ath-next 8e0ab5b9adb7
>   - converted missing call sites ath12k_wmi_obss_color_collision_event()
>     & ath12k_wmi_pdev_temperature_event()
>   - changed alloc order & cleanup path in ath12k_core_alloc() as it seems
>     it confused people
>   - used sizeof(*tb) in ath12k_wmi_tlv_parse()
> 
> Note I did try to move to a DEFINE_PER_CPU() allocated array but the module
> loader complained about the array size. So I stuck to the per ab alloc. 
> ---
>  drivers/net/wireless/ath/ath12k/core.c |   7 +
>  drivers/net/wireless/ath/ath12k/core.h |   2 +
>  drivers/net/wireless/ath/ath12k/wmi.c  | 178 ++++++-------------------
>  3 files changed, 51 insertions(+), 136 deletions(-)
...
> @@ -3913,7 +3903,7 @@ ath12k_wmi_obss_color_collision_event(struct ath12k_base *ab, struct sk_buff *sk
>  	u32 vdev_id, evt_type;
>  	u64 bitmap;
>  
> -	const void **tb __free(kfree) = ath12k_wmi_tlv_parse_alloc(ab, skb, GFP_ATOMIC);
> +	const void **tb = ath12k_wmi_tlv_parse(ab, skb);

checkpatch complains:
Missing a blank line after declarations

Note that when __free() is used that this rule is not enforced since __free()
declarations should appear at first use

So I'd separate the declaration of tb from the assignment to be aligned with
all the other WMI functions

>  	if (IS_ERR(tb)) {
>  		ath12k_warn(ab, "failed to parse OBSS color collision tlv %ld\n",
>  			    PTR_ERR(tb));

that's it for the nits. the development is stress testing the functionality.

/jeff