[alsa-devel] tascam us122l patch commit

[Takashi Iwai]

At Mon, 07 Oct 2013 10:29:42 +0200,
Takashi Iwai wrote:
> 
> At Sat, 5 Oct 2013 11:35:58 +0100,
> James Miller wrote:
> > 
> > Hi, I have just attempted to install the 3.10.10 realtime kernel and I have
> > discovered that the patch l listed in the following webpage :
> > 
> > http://www.remastersys.com/forums/index.php?topic=3013.60
> > 
> > doesn't seem to have made it 'upstream' (I am not particularly familiar
> > with the terminology).
> > 
> > It's simple to do by hand but I can confirm that I have been using the
> > above patch (VM_IO) on 3.8.13 and 3.10.10 kernels with success - the tascam
> > us122L works fine.
> 
> Hrm, interesting.  VM_IO must be incorrect in this case (the allocated
> buffer is real RAM pages), but it makes the device working by some
> reason.  We can't apply the patch because it's wrong, but need to
> investigate more why it apparently fixes...

I think I nailed down.  Could you try the patch below?


thanks,

Takashi

---
From: Takashi Iwai <tiwai at suse.de>
Subject: [PATCH] ALSA: usx2y, us122l: Fix pcm_usb_stream mmapping regression

The pcm_usb_stream plugin requires the mremap explicitly for the read
buffer, as it expands itself once after reading the required size.
But the commit [314e51b9: mm: kill vma flag VM_RESERVED and
mm->reserved_vm counter] converted blindly to a combination of
VM_DONTEXPAND | VM_DONTDUMP like other normal drivers, and this
resulted in the failure of mremap().

For fixing this regression, we need to remove VM_DONTEXPAND for the
read-buffer mmap.

Reported-by: James Miller <jamesstewartmiller at gmail.com>
Cc: <stable at vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/usb/usx2y/us122l.c        | 4 +++-
 sound/usb/usx2y/usx2yhwdeppcm.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/sound/usb/usx2y/us122l.c b/sound/usb/usx2y/us122l.c
index d0323a6..999550b 100644
--- a/sound/usb/usx2y/us122l.c
+++ b/sound/usb/usx2y/us122l.c
@@ -262,7 +262,9 @@ static int usb_stream_hwdep_mmap(struct snd_hwdep *hw,
 	}
 
 	area->vm_ops = &usb_stream_hwdep_vm_ops;
-	area->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+	area->vm_flags |= VM_DONTDUMP;
+	if (!read)
+		area->vm_flags |= VM_DONTEXPAND;
 	area->vm_private_data = us122l;
 	atomic_inc(&us122l->mmap_count);
 out:
diff --git a/sound/usb/usx2y/usx2yhwdeppcm.c b/sound/usb/usx2y/usx2yhwdeppcm.c
index 814d0e8..38db444 100644
--- a/sound/usb/usx2y/usx2yhwdeppcm.c
+++ b/sound/usb/usx2y/usx2yhwdeppcm.c
@@ -717,7 +717,9 @@ static int snd_usX2Y_hwdep_pcm_mmap(struct snd_hwdep * hw, struct file *filp, st
 		return -ENODEV;
 	}
 	area->vm_ops = &snd_usX2Y_hwdep_pcm_vm_ops;
-	area->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+	area->vm_flags |= VM_DONTDUMP;
+	if (!read)
+		area->vm_flags |= VM_DONTEXPAND;
 	area->vm_private_data = hw->private_data;
 	return 0;
 }
-- 
1.8.4