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

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Message-ID: <CAL_Jsq+L2W-=4m2c2zAKNAP9vsrbZkOBHUYqPevcdM9L_3xHtA@mail.gmail.com>
Date: Mon, 17 Mar 2025 12:19:23 -0500
From: Rob Herring <robh@...nel.org>
To: Jonas Gorski <jonas.gorski@...il.com>
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

On Sat, Mar 15, 2025 at 5:07 AM Jonas Gorski <jonas.gorski@...il.com> wrote:
>
> 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.

Indeed. Thanks for catching that.

Rob