Re: [PATCH] w1: simplify allocation of w1_master

[Krzysztof Kozlowski <krzk@kernel.org>]

On 24/03/2026 03:15, Rosen Penev wrote:
> Convert bus_master to a flexible array member as it's being used as one
> with the old C89 + 1 pointer trick.
> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  drivers/w1/w1_int.c | 4 +---
>  include/linux/w1.h  | 4 ++--
>  2 files changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/w1/w1_int.c b/drivers/w1/w1_int.c
> index 19a0ea28e9f3..a0bb97608564 100644
> --- a/drivers/w1/w1_int.c
> +++ b/drivers/w1/w1_int.c
> @@ -31,12 +31,10 @@ static struct w1_master *w1_alloc_dev(u32 id, int slave_count, int slave_ttl,
>  	/*
>  	 * We are in process context(kernel thread), so can sleep.
>  	 */
> -	dev = kzalloc(sizeof(struct w1_master) + sizeof(struct w1_bus_master), GFP_KERNEL);
> +	dev = kzalloc_flex(*dev, bus_master, 1);
>  	if (!dev)
>  		return NULL;
> 
> -	dev->bus_master = (struct w1_bus_master *)(dev + 1);
> -
>  	dev->owner		= THIS_MODULE;
>  	dev->max_slave_count	= slave_count;
>  	dev->slave_count	= 0;
> diff --git a/include/linux/w1.h b/include/linux/w1.h
> index 064805bfae3f..7379a9ddefc0 100644
> --- a/include/linux/w1.h
> +++ b/include/linux/w1.h
> @@ -236,9 +236,9 @@ struct w1_master {
>  	struct device_driver	*driver;
>  	struct device		dev;
> 
> -	struct w1_bus_master	*bus_master;
> -
>  	u32			seq;
> +
> +	struct w1_bus_master	bus_master[];

Code does not use it as flexible array member, does it? Why this cannot
be just two kzalloc's - one for w1_master and then next for bus_master?
Or embed it directly (composition) in w1_master?

Best regards,
Krzysztof