Hi Am 23.02.21 um 18:30 schrieb Greg KH:
On Tue, Feb 23, 2021 at 11:00:54AM -0500, Alan Stern wrote:On Tue, Feb 23, 2021 at 03:06:07PM +0100, Thomas Zimmermann wrote:Hi Am 23.02.21 um 14:44 schrieb Takashi Iwai:Aside from the discussion whether this "workaround" is needed, the use of udev->bus->controller here looks a bit suspicious. As the old USB code (before the commit 6eb0233ec2d0) indicated, it was rather usb->bus->sysdev that was used for the DMA mask, and it's also the one most of USB core code refers to. A similar question came up while fixing the same kind of bug in the media subsystem, and we concluded that bus->sysdev is a better choice.Good to hear that we're not the only ones affected by this. Wrt the original code, using sysdev makes even more sense.Hmmm, I had forgotten about this. So DMA masks aren't inherited after all, thanks to commit 6eb0233ec2d0. That leas me to wonder how well usb-storage is really working these days... The impression I get is that Greg would like the USB core to export a function which takes struct usb_interface * as argument and returns the appropriate DMA mask value. Then instead of messing around with USB internals, drm_gem_prime_import_usb could just call this new function. Adding such a utility function would be a sufficiently small change that it could go into the -stable kernels with no trouble.Yes, sorry for not being clear, that is what I think would make the most sense, then all USB drivers could use it easily and it can be changed in one location if the DMA logic ever changes.
We can certainly do that. Thanks for clarifying. I'll send out an updated patch soon.
Best regards Thomas
thanks, greg k-h _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer
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