At Thu, 23 May 2013 18:45:29 +0800, Ming Lei wrote: > > On Thu, May 23, 2013 at 6:36 PM, Takashi Iwai <ti...@suse.de> wrote: > > > > No, f/w loader always fall back to user mode helper, as long as its > > support is built in. And doing that for microcode driver in that code > > path isn't only superfluous but also broken due to request_firmware > > call in module init. > > Firstly, it is not good to do this since some distributions doesn't support > direct loading and doesn't have udevd(such as, android). > > Secondly, returning failure from request_firmware_direct() doesn't mean > the firmware doesn't exist since distribution may put the firmware other > where.
Right, the non-standard path is the problem, and basically the only problem. The distribution that doesn't support the direct loading means nothing but that. > Anyway, this example is very specific(no firmware can be accepted), and > request_firmware_nowait() should be OK for the situation. Oh no, rewriting with request_firmware_nowait() should be really the last choice. It would change the code flow awfully bad in most cases. The new kernel driver has a better firmware mechanism. If it's only the question of paths, we should move on toward that direction and drop the too complex old way. I'd vote for a warning shown when a firmware file is loaded via user mode helper (except for explicit cases like FW_ACTION_NOHOTPLUG), for example. > >> wrt. this problem, I think we > >> need to know why the direct loading is failed. > > > > The reason is obvious: the requested f/w file doesn't exist. > > And it's fine, because the microcode update is an optional operation. > > If no f/w file is found, it's not handled as an error. It just means > > that no need to update, continuing to work. > > OK, as said above, the example is very specific, and might be > workarounded by request_firmware_nowait(). It's not that easy in this case. The microcode loader driver core module doesn't invoke request_firmware() directly but it's via cpu driver. And the same callback is called in different code paths, not only at init but also via sysfs write. Thus the request_firmware() call must be synchronous there. Takashi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
