Re: [Outreachy kernel] [PATCH 1/2] staging: rtl8723bs: hal: Remove set but unused variables

["Fabio M. De Francesco" <fmdefrancesco@gmail.com>]

On Thursday, April 29, 2021 10:25:53 AM CEST Fabio Aiuto wrote:
> On Thu, Apr 29, 2021 at 09:44:47AM +0200, Fabio M. De Francesco wrote:
> > On Thursday, April 29, 2021 9:26:20 AM CEST Fabio Aiuto wrote:
> > > Hi Fabio,
> > > 
> > > On Wed, Apr 28, 2021 at 01:33:45PM +0200, Fabio M. De Francesco wrote:
> > > > Removed four set but unused variables. Issue detected by gcc.
> > > > 
> > > > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> > > > ---
> > > > 
> > > >  drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c | 5 -----
> > > >  1 file changed, 5 deletions(-)
> > > > 
> > > > diff --git a/drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c
> > > > b/drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c index
> > 
> > 082448557b53..96cb4426a0f4
> > 
> > > > 100644
> > > > --- a/drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c
> > > > +++ b/drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c
> > > > @@ -3900,14 +3900,11 @@ u8 GetHalDefVar8723B(struct adapter *padapter,
> > 
> > enum
> > 
> > > > hal_def_variable variable, v>
> > > > 
> > > >  			u32 cmd;
> > > >  			u32 ra_info1, ra_info2;
> > > >  			u32 rate_mask1, rate_mask2;
> > > > 
> > > > -			u8 curr_tx_rate, curr_tx_sgi, hight_rate,
> > 
> > lowest_rate;
> > 
> > > >  			cmd = 0x40000100 | mac_id;
> > > >  			rtw_write32(padapter,
> > 
> > REG_HMEBOX_DBG_2_8723B, cmd);
> > 
> > > >  			msleep(10);
> > > >  			ra_info1 = rtw_read32(padapter, 0x2F0);
> > > > 
> > > > -			curr_tx_rate = ra_info1&0x7F;
> > > > -			curr_tx_sgi = (ra_info1>>7)&0x01;
> > > > 
> > > >  			cmd = 0x40000400 | mac_id;
> > > >  			rtw_write32(padapter,
> > 
> > REG_HMEBOX_DBG_2_8723B, cmd);
> > 
> > > > @@ -3916,8 +3913,6 @@ u8 GetHalDefVar8723B(struct adapter *padapter, 
enum
> > > > hal_def_variable variable, v>
> > > > 
> > > >  			ra_info2 = rtw_read32(padapter, 0x2F4);
> > > >  			rate_mask1 = rtw_read32(padapter, 0x2F8);
> > > >  			rate_mask2 = rtw_read32(padapter, 0x2FC);
> > > > 
> > > > -			hight_rate = ra_info2&0xFF;
> > > > -			lowest_rate = (ra_info2>>8)  & 0xFF;
> > > > 
> > > >  		}
> > > >  		break;
> > > 
> > > rate_mask{1,2} and ra_info{1,2} seems to be unused as well.
> > > 
> > > thank you,
> > > 
> > > fabio
> > 
> > Hello Fabio,
> > 
> > I'm not sure about it: rtw_read32 calls a pointer to a function. I'm don't
> > know drivers programming, however that function looks like an 
implementation
> > of a read() system call. So I wouldn't be so sure to remove those calls.
> > 
> > Could calling a (*read) method have side effects on subsequent read()? I 
mean:
> > could it update some internal data structure? If not I can remove the
> > variables you mentioned above and the calls to read32.
> > 
> > I'm looking forward to read your reply.
> > 
> > Thanks,
> > 
> > Fabio
> 
> hi Fabio,
> 
> rtw_read32 is a macro wrapping _rtw_read32() defined as follows (in core/
rtw_io.c):
>
Hi Fabio,

Thanks a lot for your reply.

However, There is something less than clear to me... how did you find that 
rtw_read32 is a macro wrapping _rtw_read32()? I mean: I knew that, in vim, one 
can go to the definition of something by using ctrl-] key.

If I do that on rtw_read32 it takes me to a static definition of it in 
drivers/net/wireless/realtek/rtw88/hci.h. This is a one line function:

static inline void rtw_write32(struct rtw_dev *rtwdev, u32 addr, u32 val)
{       
        rtwdev->hci.ops->write32(rtwdev, addr, val);
}

When I use ctrl-] on write32() it takes me to struct rtw_hci_ops in drivers/
net/wireless/realtek/rtw88/hci.h.

After that I wanted to find where the member (*read32)() is assigned but I 
don't know where and how to grep it: I tried "grep -rn "\bwrite32\b=" drivers/
staging/rtl8723bs/" but I found nothing...

Can you please explain what I'm doing wrong in following the path I mentioned 
above and how you find out that macro?

Thanks for your time,

Fabio 
> 
> u32 _rtw_read32(struct adapter *adapter, u32 addr)
> {
>         u32 r_val;
>         /* struct       io_queue        *pio_queue = (struct io_queue
> *)adapter->pio_queue; */ struct io_priv *pio_priv = &adapter->iopriv;
>         struct  intf_hdl                *pintfhdl = &(pio_priv->intf);
>         u32 (*_read32)(struct intf_hdl *pintfhdl, u32 addr);
> 
>         _read32 = pintfhdl->io_ops._read32;
> 
>         r_val = _read32(pintfhdl, addr);
>         return rtw_le32_to_cpu(r_val);
> 
> }
> 
> the actual read seems to be performed by the handler contained in
> 
> 	pintfhdl->io_ops._read32;
> 
> so:
> 
> $ grep -r '\b_read32' drivers/staging/rtl8723bs/
> 
> drivers/staging/rtl8723bs/hal/sdio_ops.c:	ops->_read32 = 
&sdio_read32;
> 
> this is the place where _read32 is stored with sdio_read32 reference...
> 
> drivers/staging/rtl8723bs/core/rtw_io.c:	u32 (*_read32)(struct 
intf_hdl *pintfhdl, u32
> addr); drivers/staging/rtl8723bs/core/rtw_io.c:	_read32 = pintfhdl-
>io_ops._read32;
> ...
> 
> if you check it in hal/sdio_ops.c, nothing is written, just reads are
> performed (and it's not odd, for a read function isn't supposed to write
> something under the hood ;)).
> 
> I think those variables could be easily removed as W=1 gcc suggests.
> 
> thank you,
> 
> fabio