Hi,
Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx> 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 <balbi@xxxxxx>
>> ---
>>
>> 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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