Re: [RFC 13/13] USB: Disable hub-initiated LPM for comms devices.
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Am 17.05.2012 19:31, schrieb Sarah Sharp: > On Thu, May 17, 2012 at 07:07:32PM +0200, Tilman Schmidt wrote: >> >> I follow the argument for class drivers. But this patch also >> modifies drivers for specific existing USB 2.0 only devices >> which are unlikely to ever grow USB 3.0 support, such as the >> Gigaset ISDN driver: >> >>> drivers/isdn/gigaset/bas-gigaset.c | 1 + >>> drivers/isdn/gigaset/usb-gigaset.c | 1 + > > Is there a particular reason why you think that driver is unlikely to > ever get USB 3.0 support? Actually, there is. :-) - The USB devices driven by this driver aren't built anymore. - Their USB interface design is quite, um, idiosyncratic, and it's pretty unlikely that anyone will reuse it. (At least I truly hope no one will.) - Their successor models have completely different and incompatible USB interfaces which this driver is unable to handle. >> What is the interest of setting the disable_hub_initiated_lpm >> flag for these? > > It's partially to lay the foundation for anyone who wants to make a USB > 3.0 communications driver in the future. They're likely to start from > some USB 2.0 class driver, and copy a lot of code. If they notice that > flag is set in all the USB communications class drivers, they're likely > to set it as well. You've got a point there. > I'm not quite sure where the best place to provide documentation on the > flag is. I've added the kernel doc comments to the structure, but maybe > it needs to be documented somewhere in Documentation/usb/? Documentation/usb/power-management.txt would seem like a natural place. Although it appears to limit itself to "suspending" in its first paragraph, it does have a section "xHCI hardware link PM" at the end already, added by Andiry Xu on 2011-09-23. Hmmm, that section seems to suggest that LPM exists for USB2, too. Perhaps I should reconsider my attitude towards your patch. Thanks, Tilman -- Tilman Schmidt E-Mail: tilman@xxxxxxx Bonn, Germany Diese Nachricht besteht zu 100% aus wiederverwerteten Bits. Ungeöffnet mindestens haltbar bis: (siehe Rückseite)
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