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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Tony Chuang <yhchuang@realtek.com>
Cc:     "linux-wireless\@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH 5/6] rtw88: mac: remove dangerous while (1)
References: <1556879502-16211-1-git-send-email-yhchuang@realtek.com>
        <1556879502-16211-6-git-send-email-yhchuang@realtek.com>
        <87r29fkd9k.fsf@kamboji.qca.qualcomm.com>
        <F7CD281DE3E379468C6D07993EA72F84D17E871A@RTITMBSVM04.realtek.com.tw>
Date:   Fri, 03 May 2019 14:26:55 +0300
In-Reply-To: <F7CD281DE3E379468C6D07993EA72F84D17E871A@RTITMBSVM04.realtek.com.tw>
        (Tony Chuang's message of "Fri, 3 May 2019 11:22:56 +0000")
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Tony Chuang <yhchuang@realtek.com> writes:

>> 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).

Sounds good to me.

-- 
Kalle Valo