On Sat, 14 Nov 2009, Javier Kohen wrote: > On Sat, Nov 14, 2009 at 18:33, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > On Sat, 14 Nov 2009, Javier Kohen wrote: > > > >> > I tracked a problem I'm having with my USB audio DAC down to > >> > patch cb88a1b887bb8908f6e00ce29e893ea52b074940. > > > > Are you certain? That patch did not change anything important; mostly > > it just renamed some functions. > > I can't be sure, but the evidence seems to support that: > 1) I won't claim to understand this code because it's the first time I > look at it, but it seems to do more than a rename. It adds a new > callback/interface, and it moves a spinlock down within a code block. It does add a new callback interface, but it doesn't change any drivers to make them implement the new callback. Hence it won't get invoked. Two later patches, 914b701280a76f96890ad63eb0fa99bf204b961c and 7a0f0d951273eee889c2441846842348ebc00a2a, actually caused the callback to be used. So as long as neither of them is installed, I wouldn't expect the first one to make any difference. > 2) Git bisect confirmed the issue, with no bias on my part. Even > though just by looking at the changelog between versions 2.6.30.4 > (known good) and 2.6.30.8 (known bad), I had a strong hunch this patch > was the culprit. > > I don't know enough to say whether the bug is in this patch, or if > this patch just triggers it (e.g. by calling a broken callback that > wasn't being called before). What I know is that the problem didn't > happen before this patch, and it happens 100% of the time with this > patch. Are you sure you have both of the following patches installed? The third patch is necessary to fix a bug introduced by the second. > > Can you post a usbmon trace showing what happens when you run this > > test? > > Sure. They're small enough, so I've attached it to this mail. I'm also > including the output of lsusb -vv for this bus (the hub on the > monitor). Can you provide an equivalent trace with the offending patch reverted? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
