Re: [PATCH] ALSA: usb: qcom: Fix false-positive address space check

[Takashi Iwai <tiwai@suse.de>]

On Wed, 17 Sep 2025 15:59:55 +0200,
Luca Weiss wrote:
> 
> Hi Takashi,
> 
> On Wed Sep 17, 2025 at 3:09 PM CEST, Takashi Iwai wrote:
> > The sanity check previously added to uaudio_transfer_buffer_setup()
> > assumed the allocated buffer being linear-mapped.  But the buffer
> > allocated via usb_alloc_coherent() isn't always so, rather to be used
> > with (SG-)DMA API.  This leaded to a false-positive warning and the
> > driver failed to work.
> >
> > Actually uaudio_transfer_buffer_setup() deals only with the DMA-API
> > addresses for MEM_XFER_BUF type, while other callers of
> > uaudio_iommu_map() are with pages with physical addresses for
> > MEM_EVENT_RING and MEM_XFER_RING types.  So this patch splits the
> > mapping helper function to two different ones, uaudio_iommu_map() for
> > the DMA pages and uaudio_iommu_map_pa() for the latter, in order to
> > handle mapping differently for each type.  Along with it, the
> > unnecessary address check that caused probe error is dropped, too.
> 
> Thanks for fixing this, and Arnd for the help!
> 
> > Fixes: 3335a1bbd624 ("ALSA: qc_audio_offload: try to reduce address space confusion")
> > Suggested-by: Arnd Bergmann <arnd@arndb.de>
> > Acked-by: Arnd Bergmann <arnd@arndb.de>
> > Reported-and-tested-by: Luca Weiss <luca.weiss@fairphone.com>
> 
> I don't know if https://www.kernel.org/doc/html/latest/process/maintainer-tip.html
> is applicable to also sound subsystem or the whole tree but maybe
> separate tags are simpler?
> 
> Reported-by: Luca Weiss <luca.weiss@fairphone.com>
> Tested-by: Luca Weiss <luca.weiss@fairphone.com>

It's only for tip tree.
Reported-and-tested-by tag is commonly used.


Takashi