Messages in this thread | | | Date | Sun, 8 Aug 2004 10:21:33 +0200 (CEST) | From | Joerg Schilling <> | Subject | Re: PATCH: cdrecord: avoiding scsi device numbering for ide devices |
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----> This is a resend as it seems that somebody did remove linux-kernel@vger.kernel.org
>From: "H.Rosmanith (Kernel Mailing List)" <kernel@wildsau.enemy.org>
>> I can just that if you set 64KiB now, it'll be a much better alround >> value.
>very good, it works with 64kB:
> 887 /* > 888 * First try to raise the DMA limit to a moderate value that > 889 * most likely does not use up all kernel memory. > 890 */ > 891 //val = 126*1024; > 892 val = 64*1024;
>now cdrecord will happily use the scsi-linux-sg driver even for the IDE >burners connected to the "Digitus" controllers handled by the siimage driver.
So you found a nasty bug in the Linux kernel :-(
The official behavior for SG_SET_RESERVED_SIZE is:
1) You call SG_SET_RESERVED_SIZE with whatever size val you like
2) It says "thank you" and _always_ returns success
3) You call SG_GET_RESERVED_SIZE to read the value set up in the kernel. This value is not directly related to the value used with SG_SET_RESERVED_SIZE. The proposal from Douglas Gilbert was to always use 512 KB. I am unhappy with this behavior but I have to take it as it has been defined by the Author :-( He told me that the value returned with SG_GET_RESERVED_SIZE is the value available for DMA and may be much smaller than the size used with SG_SET_RESERVED_SIZE.
AGAIN: I am unhappy with this behavior but this _is_ the official behavior. If the current Linux kernel for some reasons does not behave this way it is broken and needs to be fixed.
See also: http://www.mail-archive.com/cdwrite@other.debian.org/msg00232.html
Jörg
-- EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin js@cs.tu-berlin.de (uni) If you don't have iso-8859-1 schilling@fokus.fraunhofer.de (work) chars I am J"org Schilling URL: http://www.fokus.fraunhofer.de/usr/schilling ftp://ftp.berlios.de/pub/schily - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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