[alsa-devel] [PATCH 1/2] opti93x: fix irq releasing if the irq cannot be allocated

[Takashi Iwai]

At Mon, 30 Nov 2009 20:13:09 +0100,
Krzysztof Helt wrote:
> 
> From: Krzysztof Helt <krzysztof.h1 at wp.pl>
> 
> Fix the bug that an irq is released if the irq's allocation fails.
> Move irq allocation earlier so the codec->irq is not set if the request_irq() fails. 
> 
> Signed-off-by: Krzysztof Helt <krzysztof.h1 at wp.pl>
> ---
> A different approach than the previous one.

Basically this isn't recommended in general.  The IRQ might be issued
(mistakenly, e.g. on a buggy board), the handler might access to
uninitialized ports, etc.  So, on PCI, it's definitely no-go, but on
ISA, it would work in most cases because the IRQ line is exclusive.

Another problem, however, is that code->irq is still checked for
freeing...


thanks,

Takashi


> 
>  sound/isa/opti9xx/opti92x-ad1848.c |   25 ++++++++++++++-----------
>  1 files changed, 14 insertions(+), 11 deletions(-)
> 
> diff --git a/sound/isa/opti9xx/opti92x-ad1848.c b/sound/isa/opti9xx/opti92x-ad1848.c
> index 5cd5553..fd32001 100644
> --- a/sound/isa/opti9xx/opti92x-ad1848.c
> +++ b/sound/isa/opti9xx/opti92x-ad1848.c
> @@ -558,10 +558,13 @@ __skip_mpu:
>  
>  static irqreturn_t snd_opti93x_interrupt(int irq, void *dev_id)
>  {
> -	struct snd_wss *codec = dev_id;
> -	struct snd_opti9xx *chip = codec->card->private_data;
> +	struct snd_opti9xx *chip = dev_id;
> +	struct snd_wss *codec = chip->codec;
>  	unsigned char status;
>  
> +	if (!codec)
> +		return IRQ_HANDLED;
> +
>  	status = snd_opti9xx_read(chip, OPTi9XX_MC_REG(11));
>  	if ((status & OPTi93X_IRQ_PLAYBACK) && codec->playback_substream)
>  		snd_pcm_period_elapsed(codec->playback_substream);
> @@ -690,7 +693,7 @@ static void snd_card_opti9xx_free(struct snd_card *card)
>  		struct snd_wss *codec = chip->codec;
>  		if (codec && codec->irq > 0) {
>  			disable_irq(codec->irq);
> -			free_irq(codec->irq, codec);
> +			free_irq(codec->irq, chip);
>  		}
>  #endif
>  		release_and_free_resource(chip->res_mc_base);
> @@ -738,6 +741,14 @@ static int __devinit snd_opti9xx_probe(struct snd_card *card)
>  	if (error)
>  		return error;
>  
> +#ifdef OPTi93X
> +	error = request_irq(chip->irq, snd_opti93x_interrupt,
> +			    IRQF_DISABLED, DEV_NAME" - WSS", chip);
> +	if (error < 0) {
> +		snd_printk(KERN_ERR "opti9xx: can't grab IRQ %d\n", chip->irq);
> +		return error;
> +	}
> +#endif
>  	error = snd_wss_create(card, chip->wss_base + 4, -1,
>  			       chip->irq, chip->dma1, chip->dma2,
>  #ifdef OPTi93X
> @@ -762,14 +773,6 @@ static int __devinit snd_opti9xx_probe(struct snd_card *card)
>  	if (error < 0)
>  		return error;
>  #endif
> -#ifdef OPTi93X
> -	error = request_irq(chip->irq, snd_opti93x_interrupt,
> -			    IRQF_DISABLED, DEV_NAME" - WSS", codec);
> -	if (error < 0) {
> -		snd_printk(KERN_ERR "opti9xx: can't grab IRQ %d\n", chip->irq);
> -		return error;
> -	}
> -#endif
>  	strcpy(card->driver, chip->name);
>  	sprintf(card->shortname, "OPTi %s", card->driver);
>  #if defined(CS4231) || defined(OPTi93X)
> -- 
> 1.6.4
> 
> 
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