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To: Terry Lambert <terry@lambert.org>
cc: hackers@freebsd.org, multimedia@freebsd.org
Subject: Re: mmap problems? 
In-reply-to: Your message of "Thu, 19 Dec 1996 10:10:33 MST."
             <199612191710.KAA11716@phaeton.artisoft.com> 
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Date: Fri, 20 Dec 1996 00:16:39 -0800
From: Amancio Hasty <hasty@rah.star-gate.com>
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More info,

After the mmap call from tv to the meteor driver , the system upon
a page fault calls the meteor's mmap routine or rather the first time
that I access the mmapped region. When tv fails to run, the call
to mmap is successfull however the system only calls back the meteor's
mmap routine once for the first page.

Does this make sense to anyone out there ?

	Tnks,
	Amancio


>From The Desk Of Terry Lambert :
> > > You'll have to look carefully at the driver to see which is happening
> > > (if either is the correct reason).
> 
> [ ... ]
> 
> Well, I did say "if".
> 
> Personally, I'd:
> 
> meteor_mmap(dev_t dev, int offset, int nprot)
> {
> 
>         int     unit;
>         meteor_reg_t *mtr;
> 
>         unit = UNIT(minor(dev));
> printf( "meteor_mmap: unit=%d of %d, offset=%d, nprot=%08x\n",
> 	unit, NMETEOR, offset, nprot);
>         if (unit >= NMETEOR)            /* at this point could this happen? *
/
> {
> printf( "meteor_mmap: failed: unit exceeded possible units\n");
>                 return(-1);
> }
> 
>         mtr = &(meteor[unit]);
> 
> 
>         if(nprot & PROT_EXEC)
> {
> printf("meteor_mmap: can't map a device PROT_EXEC!\n");
>                 return -1;
> }
> 
> printf("meteor_mmap: device pages(%08x)\n", mtr->alloc_pages * page_size);
>         if(offset >= mtr->alloc_pages * PAGE_SIZE)
> {
> printf("meteor_mmap: offset (%08x) exceeds device pages\n", offset);
>                 return -1;
> }
> 
>         return i386_btop(vtophys(mtr->bigbuf) + offset);
> }
> 
> This leaves a possible failure of (vtophys() + offset) to be valid;
> you can check that, but it's unlikely (the pages are wired).
> 
> 
> 					Terry Lambert
> 					terry@lambert.org
> ---
> Any opinions in this posting are my own and not those of my present
> or previous employers.