Message-ID: <43F80C15.4090409@cfl.rr.com>
Date: Sun, 19 Feb 2006 01:11:33 -0500
From: Phillip Susi <psusi@cfl.rr.com>
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To: linuxer@ever.mine.nu
CC: linux-kernel@vger.kernel.org
Subject: Re: pktcdvd DVD+RW always writes at max drive speed (not media speed)
References: <200602182023.k1IKNNuI012372@rhodes.mine.nu>
In-Reply-To: <200602182023.k1IKNNuI012372@rhodes.mine.nu>
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I thought that the code asked the drive for the max supported speed _for 
the loaded media_.  I know I've been using pktcdvd without problem on 
cdrw media that is only rated for 4x on drives that support 12x or 16x, 
and based on the performance I've been seeing, it is only burning at 4x. 
  Maybe your drive isn't reporting properly?

linuxer@ever.mine.nu wrote:
> In drivers/block/pktcdvd.c it appears that in the case of DVD
> rewriting, pkt_open_write always sets the write speed to pkt_get_max_speed
> (the maximum writing speed reported by the drive). 
> 
> In my case, I have a new drive capable of 8x re-writing. However, all of
> my existing media is rated for only 4x rewrite speed. 
> 
> When attempting to rw mount these disks, pktcdvd reports:
> 
> Feb 18 00:09:52 ever kernel: pktcdvd: write speed 11080kB/s
> Feb 18 00:09:54 ever kernel: pktcdvd: 54 01 00 00 00 00 00 00 00 00 00 00 -
> sense 00.54.9c (No sense)
> Feb 18 00:09:54 ever kernel: pktcdvd: pktcdvd0 Optimum Power Calibration failed
> 
> And then of course a huge heap of I/O errors on the disk. 
> 
> 
> pktcdvd.c only calls pkt_media_speed for CD drives, not DVD
> drives. dvd+rw-tools has a program, dvd+rw-mediainfo, that is able to derive
> the information of the rated media speed successfully. Code from this should
> be integrated into the pktcdvd driver so as to avoid this pitfall. 
> 
> However, as I don't necessarily expect someone to do this for me right
> away, I have a second question:
> 
> Although migrating sensing code from dvd+rw-mediatype would be by far the
> more elegant solution, it occurs to me that an easier hack would be to add
> a new case to pkt_ctl_ioctl, something along the lines of
> PKT_CTRL_CMD_FORCESPEED or similar, and patch pktsetup.c (simple user mode
> pktcdvd setup/teardown utility, a component provided in udftools) likewise
> to allow the user to specify the write speed. I would also have to add an
> additional member to struct pktcdvd_device in order to store this setting
> on a per device context, however. Would this work, or am I too naive about
> kernel programming?
> 
> Also, would this be a welcome or useful addition anyways (regardless of
> possible future media-speed autodetection), to allow the user to override
> and write faster/slower than drive reports media speed, to allow the user
> more flexibility in overspeed/underspeed writing based on individual media
> performance? 
> 
> Thank you for taking the time to read this, and I would appreciate any of
> your thoughts.
> 
> PS: Please CC me, as I am not currently subscribed to the list. 
> 

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