linux-kernel - Re: [PATCH v1] staging: vme_user: replace (1 << n) with BIT(n)

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Message-ID: <20251206101002.5e05bed7@pumpkin>
Date: Sat, 6 Dec 2025 10:10:02 +0000
From: David Laight <david.laight.linux@...il.com>
To: Dharanitharan R <dharanitharan725@...il.com>
Cc: gregkh@...uxfoundation.org, linux-staging@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] staging: vme_user: replace (1 << n) with BIT(n)

On Sat,  6 Dec 2025 06:36:19 +0000
Dharanitharan R <dharanitharan725@...il.com> wrote:

> In drivers/staging/vme_user/vme.c, the functions vme_register_bridge()
> and vme_unregister_bridge() use bit shifts like (1 << i) and
> (1 << bridge->num) to manipulate vme_bus_numbers.
> 
> Replace these shifts with the BIT(n) macro for readability,
> consistency, and kernel coding style.

The whole loop is just doing ffz().
So could be:
	if (vme_bus_numbers != ~0u) {
		bus_num = ffz(vme_bus_numbers);
		vme_bus_numbers = BIT(bus_num);
		bridge->num = bus_num;
		...
		ret = 0;
	}

    David
		
> 
> Changes:
> - vme_register_bridge(): (1 << i) → BIT(i)
> - vme_unregister_bridge(): (1 << bridge->num) → BIT(bridge->num)
> 
> Signed-off-by: Dharanitharan R <dharanitharan725@...il.com>
> ---
>  drivers/staging/vme_user/vme.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/vme_user/vme.c b/drivers/staging/vme_user/vme.c
> index 2095de72596a..f62a94ef35fc 100644
> --- a/drivers/staging/vme_user/vme.c
> +++ b/drivers/staging/vme_user/vme.c
> @@ -1766,8 +1766,8 @@ int vme_register_bridge(struct vme_bridge *bridge)
>  
>  	mutex_lock(&vme_buses_lock);
>  	for (i = 0; i < sizeof(vme_bus_numbers) * 8; i++) {
> -		if ((vme_bus_numbers & (1 << i)) == 0) {
> -			vme_bus_numbers |= (1 << i);
> +		if ((vme_bus_numbers & BIT(i)) == 0) {
> +			vme_bus_numbers |= BIT(i);
>  			bridge->num = i;
>  			INIT_LIST_HEAD(&bridge->devices);
>  			list_add_tail(&bridge->bus_list, &vme_bus_list);
> @@ -1787,7 +1787,7 @@ void vme_unregister_bridge(struct vme_bridge *bridge)
>  	struct vme_dev *tmp;
>  
>  	mutex_lock(&vme_buses_lock);
> -	vme_bus_numbers &= ~(1 << bridge->num);
> +	vme_bus_numbers &= ~BIT(bridge->num);
>  	list_for_each_entry_safe(vdev, tmp, &bridge->devices, bridge_list) {
>  		list_del(&vdev->drv_list);
>  		list_del(&vdev->bridge_list);