Date: Fri, 14 Aug 1998 09:29:23 -0400 From: Randall Hopper <rhh@ct.picker.com> To: "Louis A. Mamakos" <louie@TransSys.COM>, Roger Hardiman <roger@cs.strath.ac.uk> Cc: Scott Mitchell <scott@dcs.qmw.ac.uk>, Amancio Hasty <hasty@rah.star-gate.com>, multimedia@FreeBSD.ORG Subject: Re: FXTV and DGA Message-ID: <19980814092923.A6722@ct.picker.com> In-Reply-To: <199808140158.VAA11299@whizzo.transsys.com>; from Louis A. Mamakos on Thu, Aug 13, 1998 at 09:58:03PM -0400 References: <35D2E663.7AF0@cs.strath.ac.uk> <19980813160216.B6924@dcs.qmw.ac.uk> <35D31170.2781@cs.strath.ac.uk> <199808140158.VAA11299@whizzo.transsys.com>
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Louis A. Mamakos: |> The problem was basically this. |> You need to allocate configuous memory for the frame buffer. |> |> At boot time, this is easy. Memory is empty and you can allocate |> a 864k block of memory with no gaps in it. |> However, I was told that by the time the system has booted, |> and the LKM executed, there is quite possible you cannot get a |> contiguous block of memory as the memory is fragmented. ... |The alternative approach is to allocate some number of smaller (pagesize?) |buffers, and then build a command program for the Bt848 to do a scatter |read into the discountinuous buffers. This might obviate the need for |a static buffer in any case. Good idea. Some extra complexity building the RISC pgm, but a lot of benefit gained. Particularly if we could just alloc the necessary 4K pages as we need one by one on-the-fly. Don't have my bt manual here, but the only thing that comes to mind is splitting scan lines and/or pixel (e.g. packed 24bpp) on these subbuffer boundaries. I can't remember how flexible the bt848 is in dealing with this, though Amancio I'm sure knows. Worth a look though. Think the former is OK, but don't know about the latter. I wish I had the time to dig into it now, but I'm in the middle of a move/househunt/jobchg right now. Any takers? A bt848 LKM would be cool, as would not allocing the driver buffer until we open the device. A plus for BIGGENERIC inclusion. Randall To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-multimedia" in the body of the message
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