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authorStefan Richter <stefanr@s5r6.in-berlin.de>2011-08-07 15:20:18 +0200
committerStefan Richter <stefanr@s5r6.in-berlin.de>2011-08-13 13:53:30 +0200
commitaaff12039ffd812d0c8bbff50b87b6f1f09bec3e (patch)
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firewire: core: handle ack_busy when fetching the Config ROM
Some older Panasonic made camcorders (Panasonic AG-EZ30 and NV-DX110, Grundig Scenos DLC 2000) reject requests with ack_busy_X if a request is sent immediately after they sent a response to a prior transaction. This causes firewire-core to fail probing of the camcorder with "giving up on config rom for node id ...". Consequently, programs like kino or dvgrab are unaware of the presence of a camcorder. Such transaction failures happen also with the ieee1394 driver stack (of the 2.4...2.6 kernel series until 2.6.36 inclusive) but with a lower likelihood, such that kino or dvgrab are generally able to use these camcorders via the older driver stack. The cause for firewire-ohci's or firewire-core's worse behavior is not yet known. Gap count optimization in firewire-core is not the cause. Perhaps the slightly higher latency of transaction completion in the older stack plays a role. (ieee1394: AR-resp DMA context tasklet -> packet completion ktread -> user process; firewire-core: tasklet -> user process.) This change introduces retries and delays after ack_busy_X into firewire-core's Config ROM reader, such that at least firewire-core's probing and /dev/fw* creation are successful. This still leaves the problem that userland processes are facing transaction failures. gscanbus's built-in retry routines deal with them successfully, but neither kino's nor dvgrab's do ever succeed. But at least DV capture with "dvgrab -noavc -card 0" works now. Live video preview in kino works too, but not actual capture. One way to prevent Configuration ROM reading failures in application programs is to modify libraw1394 to synthesize read responses by means of firewire-core's Configuration ROM cache. This would only leave CMP and FCP transaction failures as a potential problem source for applications. Reported-and-tested-by: Thomas Seilund <tps@netmaster.dk> Reported-and-tested-by: René Fritz <rene@colorcube.de> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
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