linux-kernel - Re: [PATCH] staging: vt6656: Use defines in vnt_mac_reg_bits

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Message-ID: <20200402091917.GA17323@jiffies>
Date:   Thu, 2 Apr 2020 10:19:17 +0100
From:   Quentin Deslandes <quentin.deslandes@...ev.co.uk>
To:     Oscar Carter <oscar.carter@....com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Forest Bond <forest@...ttletooquiet.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Malcolm Priestley <tvboxspy@...il.com>,
        Amir Mahdi Ghorbanian <indigoomega021@...il.com>,
        Colin Ian King <colin.king@...onical.com>,
        Gabriela Bittencourt <gabrielabittencourt00@...il.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: vt6656: Use defines in vnt_mac_reg_bits_*
 functions

On 04/01/20 18:55:38, Oscar Carter wrote:
> On Tue, Mar 31, 2020 at 01:29:06PM +0300, Dan Carpenter wrote:
> > On Sat, Mar 28, 2020 at 10:54:33AM +0100, Oscar Carter wrote:
> > > Define the necessary bits in the CHANNEL, PAPEDELAY and GPIOCTL0
> > > registers to can use them in the calls to vnt_mac_reg_bits_on and
> > > vnt_mac_reg_bits_off functions. In this way, avoid the use of BIT()
> > > macros and clarify the code.
> > >
> > > Fixes: 3017e587e368 ("staging: vt6656: Use BIT() macro in vnt_mac_reg_bits_* functions")
> > > Suggested-by: Dan Carpenter <dan.carpenter@...cle.com>
> > > Signed-off-by: Oscar Carter <oscar.carter@....com>
> > > ---
> > >  drivers/staging/vt6656/baseband.c |  6 ++++--
> > >  drivers/staging/vt6656/card.c     |  3 +--
> > >  drivers/staging/vt6656/mac.h      | 12 ++++++++++++
> > >  drivers/staging/vt6656/main_usb.c |  2 +-
> > >  4 files changed, 18 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/staging/vt6656/baseband.c b/drivers/staging/vt6656/baseband.c
> > > index a19a563d8bcc..dd3c3bf5e8b5 100644
> > > --- a/drivers/staging/vt6656/baseband.c
> > > +++ b/drivers/staging/vt6656/baseband.c
> > > @@ -442,7 +442,8 @@ int vnt_vt3184_init(struct vnt_private *priv)
> > >  		if (ret)
> > >  			goto end;
> > >
> > > -		ret = vnt_mac_reg_bits_on(priv, MAC_REG_PAPEDELAY, BIT(0));
> > > +		ret = vnt_mac_reg_bits_on(priv, MAC_REG_PAPEDELAY,
> > > +					  PAPEDELAY_B0);
> >
> > This doesn't clarify anything.  It makes it less clear because someone
> > would assume B0 means something but it's just hiding a magic number
> > behind a meaningless define.  B0 means BIT(0) which means nothing.  So
> > now we have to jump through two hoops to find out that we don't know
> > anything.
> >
> I created this names due to the lack of information about the hardware. I
> searched but I did not find anything.
> 
> > Just leave it as-is.  Same for the rest.
> Ok.
> 
> >
> > There problem is a hardware spec which explains what this stuff is.
> >
> It's possible to find a datasheet of this hardware to make this modification
> accordingly to the correct bit names of registers ?

I haven't found any so far, if your researches are luckier than mine, I
would be interested too. Even getting your hands on the actual device is
complicated.

Thanks,
Quentin