On 03/25/2014 08:42 PM, Julius Werner wrote:
The current XHCI driver recalculates the Context Entries field in the
Slot Context on every add_endpoint() and drop_endpoint() call. In the
case of drop_endpoint(), it seems to assume that the add_flags will
always contain every endpoint for the new configuration, which is not
necessarily correct if you don't make assumptions about how the USB core
uses the add_endpoint/drop_endpoint interface (add_flags only contains
endpoints that are new additions in the new configuration).
Furthermore, EP0_FLAG is not consistently set in add_flags throughout
the lifetime of a device. This means that when all endpoints are
dropped, the Context Entries field can be set to 0 (which is invalid and
may cause a Parameter Error) or -1 (which is interpreted as 31 and
causes the driver to keep using the old, incorrect value).
The only surefire way to set this field right is to also take all
existing endpoints into account, and to force the value to 1 (meaning
only EP0 is active) if no other endpoint is found. This patch implements
that as a single step in the final check_bandwidth() call and removes
the intermediary calculations from add_endpoint() and drop_endpoint().
Hi
I think this looks good in general, but before I really dig into it I'd
like to know if this has triggered any problems so far? (e.g. slot
context's context entries getting zeroed, or set to a smaller value than
the last active endpoint context, causing trouble)
-Mathias
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