linux-kernel - Re: [PATCH v2 1/5] thermal/drivers/core: Use a char pointer for the cooling device name

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Message-ID: <18fdc11b-abda-25d9-582f-de2f9dfa2feb@arm.com>
Date:   Fri, 12 Mar 2021 18:49:43 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Jiri Pirko <jiri@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Amit Kucheria <amitk@...nel.org>,
        "open list:MELLANOX ETHERNET SWITCH DRIVERS" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] thermal/drivers/core: Use a char pointer for the
 cooling device name



On 3/12/21 5:03 PM, Daniel Lezcano wrote:
> We want to have any kind of name for the cooling devices as we do no
> longer want to rely on auto-numbering. Let's replace the cooling
> device's fixed array by a char pointer to be allocated dynamically
> when registering the cooling device, so we don't limit the length of
> the name.
> 
> Rework the error path at the same time as we have to rollback the
> allocations in case of error.
> 
> Tested with a dummy device having the name:
>   "Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch"
> 
> A village on the island of Anglesey (Wales), known to have the longest
> name in Europe.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>   .../ethernet/mellanox/mlxsw/core_thermal.c    |  2 +-
>   drivers/thermal/thermal_core.c                | 38 +++++++++++--------
>   include/linux/thermal.h                       |  2 +-
>   3 files changed, 24 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c b/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
> index bf85ce9835d7..7447c2a73cbd 100644
> --- a/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
> +++ b/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
> @@ -141,7 +141,7 @@ static int mlxsw_get_cooling_device_idx(struct mlxsw_thermal *thermal,
>   	/* Allow mlxsw thermal zone binding to an external cooling device */
>   	for (i = 0; i < ARRAY_SIZE(mlxsw_thermal_external_allowed_cdev); i++) {
>   		if (strnstr(cdev->type, mlxsw_thermal_external_allowed_cdev[i],
> -			    sizeof(cdev->type)))
> +			    strlen(cdev->type)))
>   			return 0;
>   	}
>   
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 996c038f83a4..9ef8090eb645 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -960,10 +960,7 @@ __thermal_cooling_device_register(struct device_node *np,
>   {
>   	struct thermal_cooling_device *cdev;
>   	struct thermal_zone_device *pos = NULL;
> -	int result;
> -
> -	if (type && strlen(type) >= THERMAL_NAME_LENGTH)
> -		return ERR_PTR(-EINVAL);
> +	int ret;
>   
>   	if (!ops || !ops->get_max_state || !ops->get_cur_state ||
>   	    !ops->set_cur_state)
> @@ -973,14 +970,17 @@ __thermal_cooling_device_register(struct device_node *np,
>   	if (!cdev)
>   		return ERR_PTR(-ENOMEM);
>   
> -	result = ida_simple_get(&thermal_cdev_ida, 0, 0, GFP_KERNEL);
> -	if (result < 0) {
> -		kfree(cdev);
> -		return ERR_PTR(result);
> +	ret = ida_simple_get(&thermal_cdev_ida, 0, 0, GFP_KERNEL);
> +	if (ret < 0)
> +		goto out_kfree_cdev;
> +	cdev->id = ret;
> +
> +	cdev->type = kstrdup(type ? type : "", GFP_KERNEL);
> +	if (!cdev->type) {
> +		ret = -ENOMEM;

Since we haven't called the device_register() yet, I would call here:
kfree(cdev);
and then jump

> +		goto out_ida_remove;
>   	}
>   

Other than that, LGTM

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

Regards,
Lukasz