From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Neukum Subject: Re: USB transfer_buffer allocations on 64bit systems Date: Thu, 8 Apr 2010 23:24:31 +0200 Message-ID: <201004082324.31481.oliver@neukum.org> References: Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Alan Stern Cc: Daniel Mack , linux-kernel@vger.kernel.org, Pedro Ribeiro , akpm@linux-foundation.org, Greg KH , alsa-devel@alsa-project.org, linux-usb@vger.kernel.org List-Id: alsa-devel@alsa-project.org Am Donnerstag, 8. April 2010 18:59:38 schrieb Alan Stern: > On Thu, 8 Apr 2010, Oliver Neukum wrote: > > > Am Mittwoch, 7. April 2010 17:46:17 schrieb Alan Stern: > > > Or alternatively, instead of allocating regular memory the routine > > > could simply fail. Then the caller would be responsible for checking > > > and using regular memory instead of dma-consistent memory. Of course, > > > that would put an even larger burden on the caller than just forcing it > > > to keep track of what flag to use. > > > > Then it would be sensible to pass it a filled URB, modify it or return > > an error code. > > That would work, but it doesn't match the way existing drivers use the > interface. For example, the audio driver allocates a 16-byte coherent > buffer and then uses four bytes from it for each of four different > URBs. That will not work with any fallback that does not yield a coherent buffer. Regards Oliver