netdev - Re: [PATCH] irda: fix overly long udelay()

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Date:   Fri, 25 Nov 2016 20:56:38 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     arnd@...db.de
Cc:     samuel@...tiz.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irda: fix overly long udelay()

From: Arnd Bergmann <arnd@...db.de>
Date: Thu, 24 Nov 2016 17:26:22 +0100

> irda_get_mtt() returns a hardcoded '10000' in some cases,
> and with gcc-7, we get a build error because this triggers a
> compile-time check in udelay():
> 
> drivers/net/irda/w83977af_ir.o: In function `w83977af_hard_xmit':
> w83977af_ir.c:(.text.w83977af_hard_xmit+0x14c): undefined reference to `__bad_udelay'
> 
> Older compilers did not run into this because they either did not
> completely inline the irda_get_mtt() or did not consider the
> 10000 value a constant expression.
> 
> The code has been wrong since the start of git history.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
 ...
> @@ -518,7 +518,9 @@ static netdev_tx_t w83977af_hard_xmit(struct sk_buff *skb,
>  		
>  		mtt = irda_get_mtt(skb);
>  		pr_debug("%s(%ld), mtt=%d\n", __func__ , jiffies, mtt);
> -			if (mtt)
> +			if (mtt > 1000)
> +				mdelay(mtt/1000);
> +			else if (mtt)
>  				udelay(mtt);

I know this isn't caused by you, but wow what is going on with the
indentation here?!?!?