(no subject)

(no subject)

[Eliot Blennerhassett]

The problem I am seeking help on is not an ALSA problem per-se, but as I am
working on an ALSA driver I thought I'd start here...
any suggestions for a more appropriate forum will be gratefully accepted.


Background info:
I have a lowlevel driver that works fine when I used semaphores to prevent
conention for my hardware.  Access was soley via ioctl into my driver.

I have to change the semaphore to a spinlock now that I also call basically the
same entry point from a timer routine in my ALSA driver.

When I record from the card the data is read from the card into a userspace
buffer

    ptr,size = <Buffer pointer,size received from user application>

    fs = get_fs();
    set_fs(get_ds());
    /* Ensure that the data buffer is resident in memory.  */
    if (!access_ok (wrflag ? VERIFY_WRITE : VERIFY_READ, ptr, bytes))
    {
        set_fs(fs);
        return -EFAULT;
     }

    /* Inside here is the spinlock, and a copy to the ptr mentioned above */
    HPI_MessageF (gphHpiSubsys, &hm, &hr, file );
    
    set_fs(fs);
    
Problem:
The single change from semaphore to spinlock results in a kernel panic when I
try to record from my card:
	Unable to handle kernel paging request at virtual address ...

    
Question:
Notwithstanding bad style etc, am I doing something that is fundamentally wrong
in using a userspace buffer when I am inside a spinlock i.e. in interrupt
context?  (In the same way as I must not use a semaphore in interrupt context)

Could it be that when I try to write to the buffer it causes a page fault, which
cannot be handled in interrupt context?
But I thought that access_ok call should take care of making sure the buffer is
in memory...


TIA for any insights you may have.

Eliot Blennerhassett
AudioScience Inc.
--
Junk footer beyond this point. Read at your own risk.


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Re: (no subject)

[Takashi Iwai]

At Tue, 15 Jul 2003 18:55:10 -0700 (PDT),
Eliot Blennerhassett wrote:
> 
> Question:
> Notwithstanding bad style etc, am I doing something that is fundamentally wrong
> in using a userspace buffer when I am inside a spinlock i.e. in interrupt
> context?  (In the same way as I must not use a semaphore in interrupt context)

yes.  you cannot copy_from/to_user() in the atomic situation.


Takashi


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24 bit pcm_meter ?

[Case van Rij]

I'm trying to write and/or use a meter plugin like ameter with the rme
hammerfall dsp/rme 9652 so much without much success, presumably because
of the 24 bit/non-interleaved format this card seems to internally (?) 

I noticed s16_enable( ) in alsa-lib/pcm_meter.c includes some support
for other slave pcm formats, would that (in theory) mean it should work
with the RME ? 

snd_pcm_scope_s16_open( ) does seem to work (it doesnt fail) but 
when running arecord 
pcm_mmap.c:137: snd_pcm_mmap_read_areas: 
Assertion `snd_pcm_mmap_capture_avail(pcm) >= size)`

snd_pcm_mmap_capture_avail returns 0 which shouldnt happen in
snd_pcm_mmap_read_areas() .. im trying to determine if this would be the
result of the format issue. 

So far attempts at using a plug with a fixed format as slave for ameter
have failed. 

pcm.short { 
    type plug; 
    slave { 
        pcm "hw:0,0" 
		format "S16_LE"
    }
}

pcm.ameter {
    type meter
#   slave.pcm 'hw:0,0'
    slave.pcm 'short'
    frequency 10
    scopes.0 ameter
}

Any ideas ? 

Thanks,
Case


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