> -----Original Message-----
> From: Kalle Valo <kvalo@xxxxxxxxxx>
> Sent: Monday, November 7, 2022 8:29 PM
> To: Ping-Ke Shih <pkshih@xxxxxxxxxxx>
> Cc: linux-wireless@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] wifi: rtw89: use FIELD_PREP to fill MAC quota value
>
> Ping-Ke Shih <pkshih@xxxxxxxxxxx> writes:
>
> > Coverity reported shift 16 bits could cause sign extension and might get
> > an unexpected value. Since the input values are predefined and no this
> > kind of case, original code is safe so far. But, still changing them to
> > use FIELD_PREP() will be more clear and prevent mistakes in the future.
> >
> > The original message of Coverity is:
> > Suspicious implicit sign extension: "max_cfg->cma0_dma" with type "u16"
> > (16 bits, unsigned) is promoted in "max_cfg->cma0_dma << 16" to type
> > "int" (32 bits, signed), then sign-extended to type "unsigned long"
> > (64 bits, unsigned). If "max_cfg->cma0_dma << 16" is greater than
> > 0x7FFFFFFF, the upper bits of the result will all be 1."
> >
> > Reported-by: coverity-bot <keescook+coverity-bot@xxxxxxxxxxxx>
> > Addresses-Coverity-ID: 1527095 ("Integer handling issues")
> > Fixes: e3ec7017f6a2 ("rtw89: add Realtek 802.11ax driver")
> > Signed-off-by: Ping-Ke Shih <pkshih@xxxxxxxxxxx>
> > ---
> > drivers/net/wireless/realtek/rtw89/mac.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/wireless/realtek/rtw89/mac.c b/drivers/net/wireless/realtek/rtw89/mac.c
> > index bb49033b587d2..11081dfdfb172 100644
> > --- a/drivers/net/wireless/realtek/rtw89/mac.c
> > +++ b/drivers/net/wireless/realtek/rtw89/mac.c
> > @@ -1487,10 +1487,8 @@ static int dle_mix_cfg(struct rtw89_dev *rtwdev, const struct rtw89_dle_mem *cfg
> > #define INVALID_QT_WCPU U16_MAX
> > #define SET_QUOTA_VAL(_min_x, _max_x, _module, _idx) \
> > do { \
> > - val = ((_min_x) & \
> > - B_AX_ ## _module ## _MIN_SIZE_MASK) | \
> > - (((_max_x) << 16) & \
> > - B_AX_ ## _module ## _MAX_SIZE_MASK); \
> > + val = FIELD_PREP(B_AX_ ## _module ## _MIN_SIZE_MASK, _min_x) | \
> > + FIELD_PREP(B_AX_ ## _module ## _MAX_SIZE_MASK, _max_x); \
>
> BTW in wireless nowadays the preference is to use u32_encode_bits() & co
> instead of FIELD_PREP(). Not an issue for this patch, just wanted to
> mention anyway.
>
I can practice to use u32_encode_bits() from this patch. Will send v2.
Ping-Ke
