Re: Re: [PATCH] ALSA: intel_hdmi: Check for error num after setting mask

Re: Re: [PATCH] ALSA: intel_hdmi: Check for error num after setting mask

[Jiasheng Jiang]

On Thu, Jan 06, 2022 at 04:18:01PM +0800, Takashi Iwai wrote:
> Well, 32bit DMA mask practically never fails on x86 (and other
> architectures, IIRC).  It's fine to add a sanity check, but it's
> better to be mentioned that it never fails.

Actually, I have already found many place check the 32bit DMA mask.
For example:
snd_ad1889_create() in `sound/pci/ad1889.c`, 
snd_vortex_create() in `sound/pci/au88x0/au88x0.c`
tegra_pcm_dma_allocate() in `sound/soc/tegra/tegra_pcm.c`.
Therefore, I think there must be some reason that 32bit may fail.
So, to make the system more robust, it should be better to add the
sanity check.

Sincerely thanks,
Jiang

Re: [PATCH] ALSA: intel_hdmi: Check for error num after setting mask

[Takashi Iwai]

On Thu, 06 Jan 2022 09:41:10 +0100,
Jiasheng Jiang wrote:
> 
> On Thu, Jan 06, 2022 at 04:18:01PM +0800, Takashi Iwai wrote:
> > Well, 32bit DMA mask practically never fails on x86 (and other
> > architectures, IIRC).  It's fine to add a sanity check, but it's
> > better to be mentioned that it never fails.
> 
> Actually, I have already found many place check the 32bit DMA mask.
> For example:
> snd_ad1889_create() in `sound/pci/ad1889.c`, 
> snd_vortex_create() in `sound/pci/au88x0/au88x0.c`
> tegra_pcm_dma_allocate() in `sound/soc/tegra/tegra_pcm.c`.
> Therefore, I think there must be some reason that 32bit may fail.
> So, to make the system more robust, it should be better to add the
> sanity check.

Yes, as mentioned, it's fine to add a sanity check, but it's rather
for consistency of the code, not actually fixing any real issue.
At least it's better to rephrase the commit message for avoiding
confusion for readers.


thanks,

Takashi

[PATCH] ALSA: intel_hdmi: Check for error num after setting mask

[Jiasheng Jiang]

As the dma_supported() may fail, the dma_set_mask_and_coherent() may
fail too.
Therefore, it should be better to check it and return error if fails.

Fixes: da8648097497 ("ALSA: x86: Flatten two abstraction layers")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
---
 sound/x86/intel_hdmi_audio.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/x86/intel_hdmi_audio.c b/sound/x86/intel_hdmi_audio.c
index 33b12aa67cf5..6caea517f07f 100644
--- a/sound/x86/intel_hdmi_audio.c
+++ b/sound/x86/intel_hdmi_audio.c
@@ -1770,7 +1770,9 @@ static int hdmi_lpe_audio_probe(struct platform_device *pdev)
 	card_ctx->irq = irq;
 
 	/* only 32bit addressable */
-	dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
+	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
+	if (ret)
+		goto err;
 
 	init_channel_allocations();
 
-- 
2.25.1

Re: [PATCH] ALSA: intel_hdmi: Check for error num after setting mask

[Takashi Iwai]

On Thu, 06 Jan 2022 02:24:28 +0100,
Jiasheng Jiang wrote:
> 
> As the dma_supported() may fail, the dma_set_mask_and_coherent() may
> fail too.
> Therefore, it should be better to check it and return error if fails.
> 
> Fixes: da8648097497 ("ALSA: x86: Flatten two abstraction layers")
> Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>

Well, 32bit DMA mask practically never fails on x86 (and other
architectures, IIRC).  It's fine to add a sanity check, but it's
better to be mentioned that it never fails.


thanks,

Takashi

> ---
>  sound/x86/intel_hdmi_audio.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/x86/intel_hdmi_audio.c b/sound/x86/intel_hdmi_audio.c
> index 33b12aa67cf5..6caea517f07f 100644
> --- a/sound/x86/intel_hdmi_audio.c
> +++ b/sound/x86/intel_hdmi_audio.c
> @@ -1770,7 +1770,9 @@ static int hdmi_lpe_audio_probe(struct platform_device *pdev)
>  	card_ctx->irq = irq;
>  
>  	/* only 32bit addressable */
> -	dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> +	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> +	if (ret)
> +		goto err;
>  
>  	init_channel_allocations();
>  
> -- 
> 2.25.1
>