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firewire: ohci: prevent starting of iso contexts with empty queue

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If a misguided program tried to start an isochronous context before it
has queued any packets, the call would appear to succeed, but the
context would not actually go into the running state, and the OHCI
controller would then raise an unrecoverableError interrupt because the
first Z value is zero and thus invalid.  The driver logs such errors,
but there is no mechanism to report this back to the program.

Add an explicit check so that this error can be returned synchronously.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Clemens Ladisch 2011-02-23 09:27:40 +01:00 committed by Stefan Richter
parent e81cbebdfc
commit 44b74d909d
1 changed files with 4 additions and 0 deletions
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4
drivers/firewire/ohci.c
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@ -2706,6 +2706,10 @@ static int ohci_start_iso(struct fw_iso_context *base,
u32 control = IR_CONTEXT_ISOCH_HEADER, match;
int index;
/* the controller cannot start without any queued packets */
if (ctx->context.last->branch_address == 0)
return -ENODATA;
switch (ctx->base.type) {
case FW_ISO_CONTEXT_TRANSMIT:
index = ctx - ohci->it_context_list;