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From:   Tony Chuang <yhchuang@realtek.com>
To:     Kalle Valo <kvalo@codeaurora.org>
CC:     "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: RE: [PATCH 5/6] rtw88: mac: remove dangerous while (1)
Thread-Topic: [PATCH 5/6] rtw88: mac: remove dangerous while (1)
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Date:   Fri, 3 May 2019 11:22:56 +0000
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> Subject: Re: [PATCH 5/6] rtw88: mac: remove dangerous while (1)
> 
> <yhchuang@realtek.com> writes:
> 
> > From: Yan-Hsuan Chuang <yhchuang@realtek.com>
> >
> > Not to use while (1) to parse power sequence commands in an array.
> > Put the statement (when cmd is not NULL) instead to make the loop stop
> > when the next fetched command is NULL.
> >
> > Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
> > ---
> >  drivers/net/wireless/realtek/rtw88/mac.c | 9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/wireless/realtek/rtw88/mac.c
> b/drivers/net/wireless/realtek/rtw88/mac.c
> > index 25a923b..7487b2e 100644
> > --- a/drivers/net/wireless/realtek/rtw88/mac.c
> > +++ b/drivers/net/wireless/realtek/rtw88/mac.c
> > @@ -203,17 +203,14 @@ static int rtw_pwr_seq_parser(struct rtw_dev
> *rtwdev,
> >  		return -EINVAL;
> >  	}
> >
> > -	do {
> > -		cmd = cmd_seq[idx];
> > -		if (!cmd)
> > -			break;
> > -
> > +	while ((cmd = cmd_seq[idx])) {
> >  		ret = rtw_sub_pwr_seq_parser(rtwdev, intf_mask, cut_mask, cmd);
> >  		if (ret)
> >  			return -EBUSY;
> >
> > +		/* fetch next command */
> >  		idx++;
> > -	} while (1);
> > +	};
> 
> I dount see how this is any better, with a suitable bug you can still
> have a neverending loop, right? I was thinking more something like this:
> 
> count = 100;
> do {
>     ....
> } while (count--);
> 
> That way the won't be more than 100 loops no matter how many bugs there
> are :) Of course I have no idea what would be a good value for count.
> 

To make this totally safe, I think we need to re-write the power seq parsing code.
I think I should drop this patch, and write a better code later.

And also re-write the polling command, to remove the while (1).

Yan-Hsuan