Hi, Sergei Shtylyov <[email protected]> writes: > Hello. > > On 11/4/2015 11:48 PM, Felipe Balbi wrote: > >> Just so we have some sort of documentation as to why >> we limit our Mass Storage transfers to 240 sectors, >> let's update the comment to make clearer that >> devices were found that would choke with larger >> transfers. >> >> While at that, also make sure to clarify that other >> operating systems have similar, albeit different, >> limits on mass storage transfers. >> >> Signed-off-by: Felipe Balbi <[email protected]> >> --- >> >> Guys, how about this version ? First we update comments then, >> as a follow up patch, we increase USB3 only to 2048 sectors. >> >> drivers/usb/storage/scsiglue.c | 18 +++++++++++++++++- >> 1 file changed, 17 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c >> index dba51362d2e2..00aadf3a3857 100644 >> --- a/drivers/usb/storage/scsiglue.c >> +++ b/drivers/usb/storage/scsiglue.c >> @@ -565,7 +565,23 @@ static const struct scsi_host_template >> usb_stor_host_template = { >> /* lots of sg segments can be handled */ >> .sg_tablesize = SCSI_MAX_SG_CHAIN_SEGMENTS, >> >> - /* limit the total size of a transfer to 120 KB */ >> + /* >> + * Limit the total size of a transfer to 120 KB. >> + * >> + * Some devices are known to choke with anything larger. It seems like >> + * the problem stems from the fact that original IDE controllers had >> + * only an 8-bit register to hold the number of sectors in one transfer >> + * and even those couldn't handle a full 256 sectors. >> + * >> + * Because we want to make sure we interoperate with as many devices as >> + * possible, we will maintain a 240 sector transfer size limit for USB >> + * Mass Storage devices. >> + * >> + * Tests show that other operating have similar limits with Microsoft > > Operating systems?
I'll fix this one. >> + * Windows™ 7 limitting transfers to 128 sectors for both USB2 and USB3 >> + * and Apple Mac OS X™ 10.11 limitting transfers to 256 sectors for USB2 > > Limiting as already noticed. had fixed this one before, thanks. -- balbi
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