Le Mon, 2 Feb 2015 15:39:47 +0200,
Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> a écrit :
> So apparently there were some devices that started working after the 512byte was forced?
> I wasn't involved in this at the time so I don't know the details, perhaps Alan remembers?
>
> As the patch says, USB2 specs say HS bulk endpoints only supports 512 bytes max packet size.
>
> USB2 spec section 5.8.3 Bulk Transfer Packet Size Constraints:
>
> "All Host Controllers are required to have support for 8-, 16-, 32-, and 64-byte maximum packet sizes for
> full-speed bulk endpoints and 512 bytes for high-speed bulk endpoints. No Host Controller is required to
> support larger or smaller maximum packet sizes."
>
> Or maybe that can be interpreted as 8-, 16-, 32-, 64, AND 512 bytes supported for HS bulk endpoints?
>
> I'm otherwise ok with adding the other max packet sizes as well, just worried about the original patch.
> Are we going to break something that the original patch once fixed
>
> -Mathias
If ehci driver allows to support others sizes, there may have some
devices that use it for HS.
Do you know if the windows driver allows this ?
Looking from ehci driver [1] it seems to be the case.
Instead of forbid value smaller than 512, can we have a list of
controllers that can't handle it and make it works on others ?
Does windows xhci driver allow value different of 512 for HS ?
Matthieu
[1]
ehci-q.c:
/* The USB spec says that high speed bulk endpoints
* always use 512 byte maxpacket. But some device
* vendors decided to ignore that, and MSFT is happy
* to help them do so. So now people expect to use
* such nonconformant devices with Linux too; sigh.
*/
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