Messages in this thread | | | Date | Wed, 07 Apr 2010 19:55:20 +0200 | From | Takashi Iwai <> | Subject | Re: USB transfer_buffer allocations on 64bit systems |
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At Wed, 7 Apr 2010 18:16:03 +0200, Daniel Mack wrote: > > On Wed, Apr 07, 2010 at 11:55:19AM -0400, Alan Stern wrote: > > On Wed, 7 Apr 2010, Greg KH wrote: > > > > > Alan, any objection to just using usb_buffer_alloc() for every driver? > > > Or is that too much overhead? > > > > I don't know what the overhead is. But usb_buffer_alloc() requires the > > caller to keep track of the buffer's DMA address, so it's not a simple > > plug-in replacement. In addition, the consistent memory that > > usb_buffer_alloc() provides is a scarce resource on some platforms. > > > > Writing new functions is the way to go. > > Ok, I'll write some dummies for usb_malloc() and usb_zalloc() which > will just call kmalloc() with GFP_DMA32 for now.
Can't we provide only zalloc() variant? Zero'ing doesn't cost much, and the buffer allocation shouldn't be called too often.
> And while at it, > usb_alloc_buffer() will be renamed to usb_alloc_consistent().
Most of recent functions are named with "coherent".
thanks,
Takashi
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