Re: [PATCH] clk: tenstorrent: Assign .num before accessing .hws

[Gustavo A. R. Silva]

On 9/6/26 05:48, Aamir Ahmed wrote:
> Commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with
> __counted_by") annotated the hws member of 'struct clk_hw_onecell_data'
> with __counted_by, which informs the bounds sanitizer (UBSAN_BOUNDS)
> about the number of elements in .hws[], so that it can warn when .hws[]
> is accessed out of bounds. As noted in that change, the __counted_by
> member must be initialized with the number of elements before the first
> array access happens, otherwise there will be a warning from each access
> prior to the initialization because the number of elements is zero.
> This occurs in atlantis_prcm_clocks_register() due to .num being
> assigned only after every clock has been stored in .hws[]. With
> CONFIG_UBSAN_BOUNDS and a compiler that implements __counted_by (GCC
> 15.1+ or Clang 20.1+), this triggers an array-index-out-of-bounds report
> during probe, and with CONFIG_UBSAN_TRAP the first store traps so the
> clock provider never registers.
>
> Move the .num initialization to right after the allocation.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 23c8ebc95284 ("clk: tenstorrent: Add Atlantis clock controller driver")
> Assisted-by: LLM
> Signed-off-by: Aamir Ahmed <elb12345@xxxxxxxxxxxxx>

LGTM:

Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>

Also, see more comments below...

> diff --git a/drivers/clk/tenstorrent/atlantis-prcm.c b/drivers/clk/tenstorrent/atlantis-prcm.c
> index 6d4386eeb7d..a68534a295c 100644
> --- a/drivers/clk/tenstorrent/atlantis-prcm.c
> +++ b/drivers/clk/tenstorrent/atlantis-prcm.c
> @@ -796,6 +796,8 @@ static int atlantis_prcm_clocks_register(struct device *dev,
>   	if (!clk_data)
>   		return -ENOMEM;
>   
> +	clk_data->num = num_clks;

Looks like variable num_clks can be removed entirely, and just do:

clk_data->num = data->num;

Thanks
-Gustavo