On 17-02-07 14:14:30, David Laight wrote: > From: Petko Manolov > > Sent: 07 February 2017 13:21 > ... > > > > Would you consider what David proposed (usb_control_msg_with_malloc()) > > > > for 4.11, > > > > for example? I for one will use something like that in all my drivers. > > > > > > Sure, but you might want to make it a bit smaller of a function name :) > > > > Whatever i say may be taken as volunteering. :D > > > > Second - i've got really bad taste when naming things. asdfgl() is a short > > name > > although not very descriptive. ;) > ... > > Actually, for short control transfers a field in the urb itself could be used > (unless another 8 bytes makes the structure larger). > > IIRC for xhci, the 8 byte pointer field can be marked as containing the > actual > data - saving the hardware from doing another dma as well.
Unless set up for automatic triggering, 8 byte DMA transfer is an overkill (by means of having to program a bunch of IO registers), especially on a 64bit machine. However, not knowing the USB host controllers specifics i'll shut up. cheers, Petko
