linux-kernel - RE: [PATCH] wifi: rtw89: Correct immediate cfg_len calculation for scan_offload

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Message-ID: <9d4e83ffc0d348f2965390e8dab4f25e@realtek.com>
Date: Thu, 9 Jan 2025 00:35:38 +0000
From: Ping-Ke Shih <pkshih@...ltek.com>
To: Liang Jie <buaajxlj@....com>
CC: "kvalo@...nel.org" <kvalo@...nel.org>, Bernie Huang <phhuang@...ltek.com>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Liang Jie
	<liangjie@...iang.com>
Subject: RE: [PATCH] wifi: rtw89: Correct immediate cfg_len calculation for scan_offload_be

Liang Jie <buaajxlj@....com> wrote: 
> From: Liang Jie <liangjie@...iang.com>
> 
> This patch ensures the correct calculation of `cfg_len` prior to the

No "This patch". Just in imperative tense -- "Ensure ..."

> allocation of the skb in the `rtw89_fw_h2c_scan_offload_be` function,
> particularly when the `SCAN_OFFLOAD_BE_V0` firmware feature is enabled.
> It addresses an issue where an incorrect skb size might be allocated
> due to a delayed setting of `cfg_len`, potentially leading to memory
> inefficiencies.
> 
> By moving the conditional check and assignment of `cfg_len` before skb
> allocation, the patch guarantees that `len`, which depends on `cfg_len`,
> is accurately computed, ensuring proper skb size and preventing any
> unnecessary memory reservation for firmware operations not supporting
> beyond the `w8` member of the command data structure.
> 
> This correction helps to optimize memory usage and maintain consistent
> behavior across different firmware versions.
> 
> Fixes: 6ca6b918f280 ("wifi: rtw89: 8922a: Add new fields for scan offload H2C command")
> 

No this blank line. 

> Signed-off-by: Liang Jie <liangjie@...iang.com>
> ---
>  drivers/net/wireless/realtek/rtw89/fw.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtw89/fw.c b/drivers/net/wireless/realtek/rtw89/fw.c
> index 2191c037d72e..5eb4beb9e485 100644
> --- a/drivers/net/wireless/realtek/rtw89/fw.c
> +++ b/drivers/net/wireless/realtek/rtw89/fw.c
> @@ -5169,7 +5169,7 @@ int rtw89_fw_h2c_scan_offload_be(struct rtw89_dev *rtwdev,
>         u8 macc_role_size = sizeof(*macc_role) * option->num_macc_role;
>         u8 opch_size = sizeof(*opch) * option->num_opch;
>         u8 probe_id[NUM_NL80211_BANDS];
> -       u8 cfg_len = sizeof(*h2c);
> +       u8 cfg_len;

In fact, SCAN_OFFLOAD_BE_V0 means `old` format used by `old' firmware version,
which isn't a main flow. I prefer to keep here unchanged, and modify cfg_len
along with SCAN_OFFLOAD_BE_V0 for v0 firmware. 

As existing patterns, this will be

	u8 cfg_len = sizeof(*h2c);
	u8 ver = U8_MAX;

	if (RTW89_CHK_FW_FEATURE(SCAN_OFFLOAD_BE_V0, &rtwdev->fw))
		ver = 0;

	...

	if (ver == 0)
		cfg_len = offsetofend(typeof(*h2c), w8);

	...

	if (ver == 0)
		goto flex_member;

	...


>         unsigned int cond;
>         void *ptr;
>         int ret;
> @@ -5178,6 +5178,11 @@ int rtw89_fw_h2c_scan_offload_be(struct rtw89_dev *rtwdev,
> 
>         rtw89_scan_get_6g_disabled_chan(rtwdev, option);
> 
> +       if (RTW89_CHK_FW_FEATURE(SCAN_OFFLOAD_BE_V0, &rtwdev->fw))
> +               cfg_len = offsetofend(typeof(*h2c), w8);
> +       else
> +               cfg_len = sizeof(*h2c);
> +
>         len = cfg_len + macc_role_size + opch_size;
>         skb = rtw89_fw_h2c_alloc_skb_with_hdr(rtwdev, len);
>         if (!skb) {
> @@ -5246,10 +5251,8 @@ int rtw89_fw_h2c_scan_offload_be(struct rtw89_dev *rtwdev,
>                                            RTW89_H2C_SCANOFLD_BE_W8_PROBE_RATE_6GHZ);
>         }
> 
> -       if (RTW89_CHK_FW_FEATURE(SCAN_OFFLOAD_BE_V0, &rtwdev->fw)) {
> -               cfg_len = offsetofend(typeof(*h2c), w8);
> +       if (RTW89_CHK_FW_FEATURE(SCAN_OFFLOAD_BE_V0, &rtwdev->fw))
>                 goto flex_member;
> -       }
> 
>         h2c->w9 = le32_encode_bits(sizeof(*h2c) / sizeof(h2c->w0),
>                                    RTW89_H2C_SCANOFLD_BE_W9_SIZE_CFG) |
> --
> 2.25.1