From owner-freebsd-hackers  Wed Aug  9  8:51:10 2000
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From: Soren Schmidt <sos@freebsd.dk>
Message-Id: <200008091551.RAA77500@freebsd.dk>
Subject: Re: In-kernel ioctl calls
In-Reply-To: <001e01c0020c$d257b3c0$19e55982@student.utwente.nl> from Theo van Klaveren at "Aug 9, 2000 04:19:25 pm"
To: t.vanklaveren@student.utwente.nl (Theo van Klaveren)
Date: Wed, 9 Aug 2000 17:51:02 +0200 (CEST)
Cc: freebsd-hackers@FreeBSD.ORG
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It seems Theo van Klaveren wrote:
> 
> I think I've finally figured out why AudioFS isn't working (aside from an
> endianess error in v0.1), but I can't think of a solution. The problem I've
> found is as follows: The code in atapi-cd.c (from Soren's ATA driver)
> assumes the passed buffer (in the ioctl struct) is in user-space. The
> following is the offending piece of code from the CDIOCREADAUDIO ioctl call:
> 
> --- snip ---
>   if ((error = atapi_queue_cmd(cdp->atp, ccb, buffer, size,
>           ATPR_F_READ, 30, NULL,NULL)))
>       break;
> 
>   if ((error = copyout(buffer, ubuf, size)))
>       break;
> --- snip ---
> 
> The first statement issues the read command to the device, I presume. It
> copies the data to an internal (kernel-space) buffer. Next, the internal
> buffer is copyout()ed to ubuf (which is my ioctl buffer), which fails
> because in the case of AudioFS it's in kernel space.
> 
> Boing, break, abort, no data for you. Bad boy.
> 
> This, of course, caused the buffer's data not to be initialized, causing
> noise and crackles. And AudioFS didn't know the ioctl call failed, because
> the driver didn't return an error.
> 
> Am I just doing it wrong, or should atapi-cd.c be patched to verify if the
> buffer is in user space or in kernel space? If so, what function checks if
> an address is in kernel space or in user space? If not, what am I doing
> wrong?

Here's another idea, the ata driver can read/write 2352 sector size
blocks directly, no need to use that ugly ioctl. You just have to
set the right blocksize, I could provide you with a function for
that, no more ioctl mess ;)

-Søren


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