linux-kernel - Re: [PATCH v2] wifi: ath10k: Drop of_get

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Message-ID: <CAOiHx=mr+MFE_7Krue4BPrtvtyJW0pWUBXCrqbViVH5oOTT2Hw@mail.gmail.com>
Date: Sat, 15 Mar 2025 11:07:26 +0100
From: Jonas Gorski <jonas.gorski@...il.com>
To: "Rob Herring (Arm)" <robh@...nel.org>
Cc: Kalle Valo <kvalo@...nel.org>, Jeff Johnson <jjohnson@...nel.org>, 
	linux-wireless@...r.kernel.org, ath10k@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] wifi: ath10k: Drop of_get_property() call

Hi,

On Sat, Mar 15, 2025 at 12:39 AM Rob Herring (Arm) <robh@...nel.org> wrote:
>
> There's no need to check the property presence and length before calling
> of_property_read_u8_array() as it will return an error if the property
> is missing or the length is too small. The return errno doesn't matter
> to the caller, so no change in behavior there.
>
> Change of_property_read_u8_array() to of_property_read_variable_u8_array()
> as the former allows properties to be longer than the requested length.
> Now the property has to be the exact length requested as the removed
> check required.
>
> This part of a larger effort to remove DT functions like
> of_get_property() and of_find_property() which return raw DT data
> having no reference counting.
>
> Signed-off-by: Rob Herring (Arm) <robh@...nel.org>
> ---
> v2:
>  - Add check that cal_data_len is non-zero
> ---
>  drivers/net/wireless/ath/ath10k/core.c | 24 +++++++-----------------
>  1 file changed, 7 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/core.c b/drivers/net/wireless/ath/ath10k/core.c
> index b3294287bce1..47206b171aa5 100644
> --- a/drivers/net/wireless/ath/ath10k/core.c
> +++ b/drivers/net/wireless/ath/ath10k/core.c
> @@ -1889,39 +1889,29 @@ static int ath10k_download_cal_file(struct ath10k *ar,
>  static int ath10k_download_cal_dt(struct ath10k *ar, const char *dt_name)
>  {
>         struct device_node *node;
> -       int data_len;
> +       int data_len = ar->hw_params.cal_data_len;
>         void *data;
>         int ret;
>
>         node = ar->dev->of_node;
> -       if (!node)
> +       if (!node || !data_len)
>                 /* Device Tree is optional, don't print any warnings if
>                  * there's no node for ath10k.
>                  */
>                 return -ENOENT;
>
> -       if (!of_get_property(node, dt_name, &data_len)) {
> -               /* The calibration data node is optional */
> -               return -ENOENT;
> -       }
> -
> -       if (data_len != ar->hw_params.cal_data_len) {
> -               ath10k_warn(ar, "invalid calibration data length in DT: %d\n",
> -                           data_len);
> -               ret = -EMSGSIZE;
> -               goto out;
> -       }
> -
>         data = kmalloc(data_len, GFP_KERNEL);
>         if (!data) {
>                 ret = -ENOMEM;
>                 goto out;
>         }
>
> -       ret = of_property_read_u8_array(node, dt_name, data, data_len);
> +       ret = of_property_read_variable_u8_array(node, dt_name, data, data_len, data_len);
>         if (ret) {

of_property_read_u8_array() returns 0 on success, but
of_property_read_variable_u8_array() returns the number of elements
read on success, so this check needs to be ret < 0 now.

> -               ath10k_warn(ar, "failed to read calibration data from DT: %d\n",
> -                           ret);
> +               /* Don't warn if optional property not found  */
> +               if (ret != -EINVAL)
> +                       ath10k_warn(ar, "failed to read calibration data from DT: %d\n",
> +                                   ret);

Best regards,
Jonas