From 44b74d909dc943fd9384930a141450cb17133511 Mon Sep 17 00:00:00 2001 From: Clemens Ladisch Date: Wed, 23 Feb 2011 09:27:40 +0100 Subject: [PATCH] firewire: ohci: prevent starting of iso contexts with empty queue 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 Signed-off-by: Stefan Richter --- drivers/firewire/ohci.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c index f1497b1fcf2e..c0572283b93e 100644 --- a/drivers/firewire/ohci.c +++ b/drivers/firewire/ohci.c @@ -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;