linux-kernel - Re: [PATCH 7/7] arch/unicore32/kernel/dma.c: ensure arguments to request_irq and free

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Date:	Thu, 15 Mar 2012 09:01:24 +0800
From:	Guan Xuetao <gxt@...c.pku.edu.cn>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] arch/unicore32/kernel/dma.c: ensure arguments to
 request_irq and free_irq are compatible

On Wed, 2012-03-14 at 10:23 +0100, Julia Lawall wrote:
> 
> On Wed, 14 Mar 2012, Guan Xuetao wrote:
> 
> > On Wed, 2012-03-14 at 11:19 +0300, Dan Carpenter wrote:
> >> On Wed, Mar 14, 2012 at 04:07:24PM +0800, Guan Xuetao wrote:
> >>> puv3_init_dma() is called ONCE when initializing.
> >>> In logical, if request_irq(IRQ_DMAERR, *) failed, free_irq(IRQ_DMA, *)
> >>> is unnecessary, and dma device/driver can keep on working.
> >>> The patch could be:
> >>>   	ret = request_irq(IRQ_DMAERR, dma_err_handler, 0, "DMAERR", NULL);
> >>>   	if (ret) {
> >>>   		printk(KERN_CRIT "Can't register IRQ for DMAERR\n");
> >>>  -		free_irq(IRQ_DMA, "DMA");
> >>>   		return ret;
> >>>   	}
> >>
> >> It seems like you should remove the error return as well?
> >>
> >> regards,
> >> dan carpenter
> >>
> > The error return value will only generate an extra warning message, and
> > have no side-effect.
> 
> The whole thing seems a little strange.  I guess your point is that the 
> call site never looks at the return value?  Wouldn't it be better to make 
> there be no return value in that case?  If there is a return value, some 
> calling context in the future might take that into account and then the 
> lack of a free_irq would be a memory leak.  Also if the first request_irq 
> can never fail, perhaps that should be made explicit by not testing the 
> return value?
> 
> julia
This function is an init_call, not a probe function, and it is only
called ONCE.
The dma device here has two interrupts, one IRQ_DMA, another IRQ_DMAERR.
And the device could work without IRQ_DMAERR.
The return value should indicate whether there is something wrong during
initialization, so the function needs return errno when any request_irq
is failed.
For the first request_irq, some code has prepared its resources before
this call, so I suppose it successful. However, the return value must be
tested.

Regards,
Guan Xuetao


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