On Thu, Jul 08, 2004 at 02:40:47PM -0700, Steve Calfee wrote: > > > > >From: Matthew Dharm <[EMAIL PROTECTED]> (by way of Steve > >Calfee <[EMAIL PROTECTED]>) > >To: [EMAIL PROTECTED] > >Subject: Re: [usb-storage] Re: [linux-usb-devel] Re: YEAH! (was: > >[Linux-usb-users] Genesys-Based Devices and Nforce2 usb chipset) > >Date: Thu, 08 Jul 2004 14:34:42 -0700 > > > >On Thu, Jul 08, 2004 at 10:41:15PM +0200, Oliver Neukum wrote: > >> Am Donnerstag, 8. Juli 2004 19:52 schrieb Alan Stern: > >> > KB because he thought it had to be a power of 2, maybe he had some > >> > stronger reason, or maybe he thought the sector size was 1024 rather > >than > >> > 512. (I should try asking; who knows, they might even answer...) > >> > >> Is it always 512, even on an optical drive? > > > >I've heard of opticals with sectors up to 2048. > > > >Matt > > > >From the usb 2.0 spec: > > 5.8.3 Bulk Transfer Packet Size Constraints > An endpoint for bulk transfers specifies the maximum data payload size that > the endpoint can accept from > or transmit to the bus. The USB defines the allowable maximum bulk data > payload sizes to be only 8, 16, > 32, or 64 bytes for full-speed endpoints and 512 bytes for high-speed > endpoints. A low-speed device must > not have bulk endpoints. This maximum applies to the data payloads of the > data packets; i.e., the size > specified is for the data field of the packet as defined in Chapter 8, not > including other protocol-required > information. > > So the max sector size is 512 bytes.
max packet size and max sector size are different things entirely. The USB
specs do not address the sector size (the base storage unit of the device
on the other end of the wire).
Matt
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Matthew Dharm Home: [EMAIL PROTECTED]
Maintainer, Linux USB Mass Storage Driver
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User Friendly, 10/11/1998
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