Date: Mon, 7 Mar 2005 12:53:51 +0900 From: Pyun YongHyeon <yongari@kt-is.co.kr> To: Mathew Kanner <mat@cnd.mcgill.ca> Cc: Alexander Leidinger <Alexander@Leidinger.net> Subject: Re: uaudio patch, configurable buffer size Message-ID: <20050307035351.GD951@kt-is.co.kr> In-Reply-To: <20050307032823.GH4237@cnd.mcgill.ca> References: <20050305224005.GC4237@cnd.mcgill.ca> <20050306162811.694d9c82@Magellan.Leidinger.net> <20050307025927.GB951@kt-is.co.kr> <20050307032823.GH4237@cnd.mcgill.ca>
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On Sun, Mar 06, 2005 at 10:28:23PM -0500, Mathew Kanner wrote: [...] > Per your other e-mail, as present in the source, is having the > default size of 16*1024 and doing bus_dma_tag_create with a maxsegz of > 0x3fff (16*1024-1) a bug? I think so. I couldn't verify it since I don't have real hardware and don't know USB audio internals. But I believe almost all audio hardwares can transfer upto 64KB in a single DMA request. Many device drivers for PCI audio cards use 0x3ffff(256KB - 1). I don't know those hardwares can transfer upto that huge size and hardly believe this. But pcm(4) further restricts the buffer size to 64KB in pcm_getbuffersize and we created DMA tag with single segment, so it would be OK to use 0x3ffff. -- Regards, Pyun YongHyeon http://www.kr.freebsd.org/~yongari | yongari@freebsd.org
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