From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: Warning: about not setting max_sectors Date: Tue, 10 Dec 2002 13:23:48 +0000 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20021210132348.A31628@infradead.org> References: <200212091455.gB9Etg601956@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <200212091455.gB9Etg601956@localhost.localdomain>; from James.Bottomley@steeleye.com on Mon, Dec 09, 2002 at 08:55:41AM -0600 List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: linux-scsi@vger.kernel.org On Mon, Dec 09, 2002 at 08:55:41AM -0600, James Bottomley wrote: > For some reason, the SCSI core is now warning about drivers which don't set > max_sectors. > > Just for the record, we have two parameters in the template: > > sg_tablesize which determines the maximum number of scatter gather entries the > host can have (corresponds to max_phys_segments in the block layer), and > > max_sectors, which imposes a maximum overall transfer length (corresponds to > max_sectors in the block queue). > > The comments over max_sectors list it as optional (if unset, we set it to the > scsi equivalent of machine infinity---well, actually 1024, or 512Mb for usual > blocks). > > The reason it's unset on so many drivers is that usually, they have no > absolute transfer limit, so they're just bounded by the number of entries in > the scatter-gather list. > > I can't see a reason to force every driver suddenly to have an arbitrary > max_sectors, so if no-one objects, I'll pull out the warning. I added this intentionally. The default is set in scsi_register_host which is an obsolete interface. This warning reminds driver writers to set the value explicitly, with scsi_add_host & friends they won't get a default anymore.